Category Archives: Invitation Submit For Anyone Who Sees A Mistake To Tear This To Pieces

Epistemically Accessible Possible Worlds, Compatibility, Failure Of Bivalence, And Inconsistent Situations

Caravaggio’s painting the CARDSHARPS nicely encapsulates the structure of a situation, and illustrates the three-place relation Rstu. Situations and their structure I will be discussing extensively in this essay in order to arrive at a satisfactory statement of the truth conditions for negation. This statement will be needed to resolve the paradoxes of Classical Logic’s Material Implication, paradoxes which Strict Implication does not completely resolve. Rstu I will be discussing in a different essay

I start by attempting to define situations (as opposed to possible worlds) in terms of parts of possible worlds that are epistemically accessible to me from my situation in the actual world. This will let me show how A v ~A can be false for a situation. In other words, both A and ~ A are false for that situation, though not for a possible world. The situation therefore counts as non-bivalent. I will show this by way of a set of truth conditions for negation that rely on a concept of a compatibility relation between situations that relies on possible worlds that are epistemically accessible from the actual world for a sentient being S.

I will then add ‘ostensible objects’ to my account of situations. This will let me show how ‘A and not A‘ can be true for a situation, a situation that would therefore count as inconsistent. I will show this employing a concept of an incompatibility relation between situations that relies on (impossible?) worlds that are epistemically inaccessible from the actual world for a sentient being S.

Both non-bivalent and inconsistent situations are needed for Relevant Logic, a paraconsistent logic, in order to eliminate countless irrelevant implication propositions that would otherwise be true.

I am willing to ‘go there’, so to speak, because I will do practically anything (even becoming one of those squeegee car-window washers waiting to pounce on cars at intersections in the hopes of gaining a quarter) to avoid making the following true:

If Cliff lives in Houston, then the earth has at least one moon

If Paris, Texas is the capital of France, then Calypso music originated in Wisconsin

If I vote for Hillary Clinton, we will end up with a criminal president who is under investigation from day one

All of the above statements are true in Classical Logic but false in Relevant Logic.

Let me start, then.

Nota Bene: in what follows, I will be enclosing the names of words and phrases in double quotes, and the names of concepts, relations, and propositions within single quotes. I will use | to mean “alternatively”. The first occurrence of an important technical term will be in bolded italic.

Although the contents of this paragraph will probably seem a bit opaque to a reader who is not already familiar with these issues, I will list out anyway the points I will be making here. We can analyze ‘compatibility’/’incompatibility’ in terms of (parts of) epistemic possible worlds. We do not need to leave these concepts as primitives. Since, as it will turn out, situations have everything to do with knowledge/information, it should not surprise us that the concept ‘epistemic possible world’, as well as related epistemic concepts, should be useful for analyzing them. The method I employ in the following will itself also rely heavily on the concept of epistemic possible worlds. All of the above will be used to analyze a truth condition for negation that will allow for the existence of situations that fail to bivalent and that fail to be consistent. And ultimately, of course (though I will not be discussing this in detail here), the aim of doing that is to show how the above implications can be regarded as false.

Here is the crumb-trail for this disquisition. First I will be discussing possible worlds in general, then possible worlds that are epistemically accessible for an agent S from another possible world (especially the actual world). I will then discuss situations, which discussion will branch off into two streams. In one stream, I will discuss what in a situation (as opposed to a possible world) is truth-making for a sentence. In the other stream, I will discuss the binary compatible/incompatible relation among situations. These two streams will converge in a statement of the truth condition for negation, which is (spoiler alert) as follows:

A situation makes ~A true if and only if every situation compatible with it fails to make A true

RL p. 75

This truth condition for negation will then let me show how situations can fail to be bivalent and fail to be consistent. The discussion of inconsistent situations will include a discussion of ostensible objects.

But to get to this truth condition, I will need to discuss what it means to “make” a sentence true, and what it means to say one situation is compatible with another. And in turn, to get to those discussions, I will need to discuss possible worlds, and those parts of possible worlds called “situations”.

Here are the topics I will be discussing, in order: Possible Worlds Spawned-From-The-Known Possible Worlds Spawned-From-The-Unknown Possible Worlds Possible Worlds That Are Epistemically Accessible To Me From The Actual World Situations Epistemic Possibility Epistemic Truth Compatibility/Incompatibility Situations Drawn From Spawned-From-The-Unknown Possible Worlds Situations Drawn From Spawned-From-The-Known Possible Worlds Bivalent and Inconsistent Situations Making A True

Possible Worlds

At least for now — until I am forced to change — I will take a possible world to be defined by a set of natural-language descriptions, each one of which corresponds | fails to correspond to a state of affairs which, because it obtains | fails to obtain at a time t, is (to follow Chisholm) identical with a proposition. There is therefore a one-to-one relationship between a state of affairs and a proposition that obtains | fails to obtain at t. There is, of course, a many-to-one relationship between natural-language descriptions and a proposition aka state of affairs at t. “Umuulan” uttered in Manila as one holds an umbrella and “It is raining” also uttered in Manila while holding an umbrella are natural-language descriptions in Tagalog and English respectively which both express the proposition named by ‘it is raining’.

A sufficient condition for a state of affairs’ obtaining is its having a set of objects located in space-time and bearing the relevant relations to one another. For example, the state of affairs expressed by the sentence “Our Unix SA is standing to Genghis Khan’s right; and my brother Dan is standing to Leon Trotsky’s left who in turn is standing to Genghis Khan’s left” obtains if our Unix SA, Genghis Khan, Dan, and Leon Trotsky have a location in space-time at t and are spatially related to one another in the way just described.

The description that expresses the proposition are sentences in a natural language that are used to perform a speech act of describing. If my cat Tiger is now sitting on the mat in my apartment, that state of affairs obtains, and the description performed by uttering the English sentence “My cat Tiger is now sitting on the mat” expresses a proposition that is true because it corresponds to this state of affairs. In a derivative way, the description/sentence also corresponds to this state of affairs and is also true. If Tiger is not now sitting on this mat, the aforementioned state of affairs does not now obtain, and the aforementioned proposition does not correspond to anything in my apartment that would make it true. The proposition is false, as is the sentence expressing that proposition whose utterance performs the speech act of making a false description.

I will leave ‘state of affairs’ as an unanalyzed primitive, explicating it only by providing examples. ‘Corresponds’ I will also not say much about, except to say that it is a relation between a proposition and a state of affairs, and the relation might be, as Chisholm thinks, identity at a time t.

As one possible world among others (if something is actual, it is also possible), the actual world comprises that set of descriptions, each one of which expresses a proposition that corresponds to a state of affairs that obtains. In the actual world, the color of the walls in my apartment is a nice, subtle portobello mushroom. The description “my apartment has portobello-mushroom colored walls” corresponds to this particular state of affairs, this particular piece of the actual world. It is a member of the set of descriptions that defines the actual world. I will say that the description maps to the state of affairs. I conceive of states of affairs that obtain as akin to bricks building up the actual world.

In the actual world the color of the walls in my apartment is not a wild fuchsia. The description “fuchsia-colored walls” does not correspond to this particular piece of the actual world. That this state of affairs fails to obtain (i.e., my apartment walls being wild fuchsia) means that it is not part of the actual world. The actual world contains just the one portobello mushroom brick, so to speak, and not a fuchsia brick.

Spawned-from-the-known possible worlds. Through a kind of wave of the hand, I can specify a possible world distinct from the actual world by saying “everything is the same as in the actual world, except the color of the walls of my apartment is a wild fuchsia.” In doing this, I have just spawned, so to speak, or “accessed” a possible world (which, henceforth, I will call the “fuchsia-wall possible world”) by taking a description of a state of affairs I know to obtain in the actual world (“the walls of my apartment are a nice subtle portobello mushroom”), a state of affairs that is exposed to me, so to speak, and substituting for it a different description (“the walls of my apartment are a wild fuchsia”), a description which fails to map to any obtaining state of affairs in the actual world. I will call possible worlds accessed this way “spawned-from-the-known possible worlds.”

These possible worlds are defined by sets of descriptions some of which map to the states of affairs that “build up” so to speak the actual world and others which do not map to or correspond to any states of affairs obtaining in the actual world. When a description does correspond to a state of affairs obtaining at t in the actual world, I will say that the description is satisfied by the state of affairs.

A state of affairs is actual when the objects it comprises have a location in space time. For all I know, there may be more than one space-times. Here, however, I will assume there is just one, and that there is, therefore, just one actual world comprising all actual states of affairs. will assume that there is only one actual world. The actual world is one possible world among others, but it is the only one in which every description in the set of descriptions that defines it maps to the corresponding state of affairs which obtains.

If I may be allowed to indulge in wild metaphor for the moment, I will say that the fuchsia-wall possible world is composed of the same bricks as the actual world, with the exception that the portobello mushroom brick has been taken out and replaced with a written note saying “this is a fuchsia brick”.

I will call phrases such as “fuchsia walls” “key descriptions”, since these are the descriptions that, with the aid of the “everything else is the same” hand wave, are key to defining the fuchsia-wall possible world and opening up so to speak that world to me. It will be seen shortly that key descriptions are not limited to generating or “accessing” spawned-from-the-known possible worlds. When a key description is not satisfied by a state of affairs in the actual world, I will say that the content of that description is merely “posited“.

A positing may be actually realized by a person performing it, or it could be something potentially realized. An hour ago, for example, I had not posited a butterfly with black and white wings fluttering about in the Amazon at GPS location xyz, but I am now. An hour ago this particular possible world was just a potential one, contemplated perhaps by an infinite mind but by no one else. Compare this notion with that of a line in geometry that, potentially, is infinitely divisible, but each of whose segments is known by an infinite mind.

While I am still here, let me “access” (henceforth I will not be placing scare quotes around the word “access”) a couple more spawned-from-the-known possible worlds. I can say “everything is the same (even the color of my apartment walls) as in the actual world mutatis mutandis, except that water flows uphill.” Again, I have “generated” or accessed a possible world from a known fact in the actual world, namely, that water flows downhill. Or: “everything is the same as in the actual world, except that donkeys talk”. I have accessed a possible world by using a known fact in the actual world namely, that donkeys don’t talk. Naturally, the “mutatis mutandis” (would very much else really be the same if donkeys talked or water ran uphill?) makes me a bit uncomfortable, but I won’t try to deal here with the issues it may raise.

Spawned-from-the-unknown possible worlds. I can access a possible world, though not one necessarily distinct from the actual world, by using as my raw material a piece of the actual world about which I do not have knowledge. Suppose, for example, that, in the Pilsen neighborhood of Chicago, near Western Avenue, Elizarraraz (from whom I was renting living quarters and studio space for a while … “Elizarraraz” is Ladino, the Iberian Sephardic counterpart to the Ashkenazim Yiddish, for “poor king”; many people of Jewish descent managed to make their way to Mexico, from which country Elizarraraz’ paternal ancestors hail, in order to place as much distance as possible between themselves and the Spanish Inquisition … but I digress) . . . as I was saying, suppose that Elizarraraz has set up a shell game comprising three shells under one of which lies a peanut. I do not know, of course, under which shell the peanut lies hidden.

Might this be the infamous rogue peanut?

I can generate three possible worlds from these three unknowns by filling in the “holes”, so to speak, with key descriptions taking the form “the peanut lies under shell #x”. In one possible world, the peanut lies under shell #1 and everything else is the same as in the actual world; in the other it lies under shell #2 and everything else is the same as in the actual world; in the third it lies under shell #3 and everything else is the same as in the actual world.

Possible Worlds That Are Epistemically Accessible To Me From The Actual World: I do not know anything that would rule out the identity of any of these possible worlds with the actual world. Following the literature, I will say that these are possible worlds that are epistemically accessible for me from my location in the actual world.

We can talk about the relation of espistemic [sic] accessibility. A world w0 is epistemically accessible from w for an agent S (in w) iff S knows nothing that would rule out the hypothesis that w0 = w. Then, p is epistemically necessary (for S) iff p is true at all possible worlds that are epistemically accessible from w (for S).

http://fitelson.org/125/accessibility.pdf

I modify the above to the following:

A world w0 is epistemically accessible from w for an agent S (in w) iff nothing in the body of knowledge possessed by S would rule out the hypothesis that w0 = w.

I want to talk about ‘a body of knowledge’ to segue more easily into a discussion of probability which I will be doing shortly. According to Henry Kyburg’s account of probability, which I find useful, a probability is always asserted relative to a body of knowledge or evidence:

My own conception of probability is, like Keynes’s and Carnap’s, a logical one. Probability statements are logically true, if they are true at all. A probability is asserted always relative to a body of evidence; relative to different bodies of evidence different probability statements will be true. … I do not want to regard this body of knowledge as fixed in any absolute sense; over a period of time, however brief it changes. But in order to clarify the process of inference we introduce the logician’s standard idealization and regard the inference as taking place at a timeless moment. In this moment there are statements are open to question and statements that are not open to question — though in another moment, or from another point of view, they could of course be questioned.

Henry E. Kyburg Jr., EPISTEMOLOGY AND INFERENCE (Minneapolis, University of Minnesota Press, 1983), p. 137

Adding to this account the claim that one does not necessarily know or even believe they know something that the they actually do know will save me a fair amount of agony and grief. A skeptic, for example might persuade me that I do not know that I am awake and not dreaming when in fact I do know that I am awake and not dreaming. Someone may be told by someone who completely convinces them for a moment “Who are you going to believe: me or your lying eyes?” [[It is possible to hold conflicting beliefs at the same time.]]

The actual world is, of course, a possible world that is epistemically accessible for me and to everyone existing in it because I, along with everyone else, know nothing that would rule out the identity of the actual world with the actual world. Since the actual world is my primary concern here, I will assume that the possible world w that S is located in and from which they access other possible worlds, is the actual world. I will sometimes replace ‘S knows nothing that would rule out the hypothesis that’ with ‘so far as S knows’ or ‘to the extent of S‘s knowledge’.

Not every spawned-from-the-unknown possible world is a possible world epistemically accessible to me from my location in the actual world. I could, for example, also generate a possible world from the three unknowns just mentioned by positing a peanut that is always, of its own accord, switching between shells and sometimes even finding itself on the nose of the Mona Lisa, mimicking thereby the possible behavior of a rogue electron as described by a chemistry TA I once had as an undergraduate. But we know things (I think … I hope) that rule out the identity with the actual world of the possible world in which peanuts behave this way: namely, that peanuts do not behave this way in the actual world. Although electrons may behave this way (if I can trust my memory of what my undergraduate chemistry TA told me), peanuts do not jump from shell to shell and they never find themselves of their own accord on the nose of the Mona Lisa. This possible world is not epistemically accessible for me from my location in the actual world.

No peanut here — so far

Possible worlds spawned from unknown pieces of the actual world, then, fall into two categories: those that are epistemically accessible for a knower S from S‘s location in the actual world (every now and then I will be referring to these just as “epistemically accessible possible worlds”), and those that are not.

The possible world w0 in which Bigfoot is roaming the forests of western Washington state is epistemically accessible for me because I know nothing that would absolutely rule out the identity of this possible world with the actual world. Likewise, the possible world w1 in which Bigfoot is not roaming the forests of western Washington state is also epistemically accessible for me because I know nothing that would rule out the identity with the actual world of this possible world. I think the chances are greater than 50% that Bigfoot is not roaming these forests, but that is not the same as my knowing this.

These two possible worlds are incompatible; they cannot be the same possible world. The one world precludes the other. One makes ‘Bigfoot is roaming…’ (A) true; the other makes ‘Bigfoot is not roaming…’ (~A) true. A possible world answers every question: for any given possible world, either Bigfoot is roaming in the possible world or she is not. One must be true but not the other. Both cannot be true. So in all possible worlds A ^ ~A is false. A possible world cannot be inconsistent.

(At least for now, I won’t try to deal with possible counter-examples to this assertion. One such possible counterexample is Graham Priest’s contention that a person walking out of a room is, for one moment, both inside the room and outside the room when the center of their gravity aligns with the center of the door space. I am tempted to think that ‘inside the room’ and ‘outside the room’ are two different situations which have a common boundary, with the result that the description “outside the room” is not always the negation of “inside the room”. But I won’t try to expand on this now. At the moment I will simply assume that in all possible worlds A ^ ~A is false.)

Which possible world we are talking about hinges on how it answers the Bigfoot question (A or not A?). The identities of w0 and w1 depend upon this answer. The identity of possible world w0 depends upon that world’s not being possible world w1. If I exist in a possible world in which A is true at a time t then all of a sudden per impossibile I am existing in a possible world in which A is not true at this same time t, then I have been transported to a different possible world. (Maybe Scottie beamed me into it.)

And one of them (at any given time), A or not A, must hold in w0 and w1. In neither world can neither ‘Bigfoot is roaming the forests of Western Washington State’ nor ‘Bigfoot is not roaming the forests of Western Washington State’ be true. The worlds must be bivalent. One or the other — at least one and at most one — A or not A, must be true for these possible worlds to be the possible worlds — mutually exclusive worlds — they are. To remove A from w0 would be to strip that world of its identity; likewise, to remove not A from w1 would be to strip that world of its identity. Neither w0 nor w1 can be a non-bivalent world. In all possible worlds, ‘A v not A‘ is true. ‘A v not A‘ is necessarily true, which means that ‘If A then A‘ is also necessarily true.

So the falsity of ‘A ^ ~A‘ and the truth of ‘A v ~A‘ stems from the criteria for the identity of possible worlds. Possible worlds have to be complete, answering every question (Is there, or is there not, a butterfly with violet wings fluttering about in the Amazon at GPS point xyz?). They have to be consistent. They must be bivalent. They would undergo serious ‘criteria of identity’ crises were these conditions not fulfilled.

To sum up this discussion of possible worlds: possible worlds fall into two categories: those possible worlds that are spawned from the known and those that are spawned from the unknown. In turn, spawned-from-the unknown possible worlds fall into two categories: possible worlds that are epistemically accessible to a sentient being S and those that are not so accessible. Unlike situations, to which I am about to turn, possible worlds must be complete (must answer every question, including what is happening at GPS point xyz in the Amazon), must be consistent, and must be bivalent.

I now turn to a discussion of situations and their compatibility/incompatibility. I will be discussing almost exclusively what I will call informational or epistemic situations, which, naturally, will be analyzed in terms of information and as parts of epistemic possible worlds. Unlike possible worlds, situations can be incomplete, inconsistent, and non-bivalent.

Situations

I now relate the concept of epistemically accessible possible worlds to the concept of a situation. A situation is a part of a possible world and comprises one or more states of affairs. A situation is not necessarily a proper part of a possible world; for I count each possible world, including especially the actual world, as a situation. Nonetheless, when I talk about situations, I will have mainly in mind situations that are proper parts of possible worlds.

Among those situations that are proper parts of a possible world are those whose states of affairs they comprise correspond to the key descriptions defining possible worlds. As we have seen, the key description “the walls of my apartment are fuchsia” defines, along with the hand-wave “and every other state of affairs is the same as in the actual world” the possible world in which the walls of my apartment are fuchsia instead of portobello mushroom. This state of affairs, had it obtained, would have had the aforementioned key description corresponding to it. I will call the situation which comprises this state of affairs a “key-description situation”.

A situation that comprises just a single state of affairs I will call a “singleton situation”. There is a many-to-one relationship between single states of affairs and the set of objects existing (actually or possibly) in whatever relationships among one another and having whatever properties. The state of affairs named by 788UIOYOIYTYTIURRRBBBB4yt76876%^%$##DYCbHGFUIYTDTFJvDIYOBOvo ‘Tiger is now sitting on the keyboard of my laptop’ FI^T%$^%DXGDIGVHLOUFC:”}{PVTDXERhjkakb sdkdvsdwlebwhcjhsasssdff is a single state affairs obtaining at t; the state of affairs named by ‘Tiger’s color is silver’ also obtains at t and is a distinct single state of affairs. There are therefore at least two singleton states of affairs here mapping to the set comprising my cat Tiger at t.

Situations that are proper parts of possible worlds are limited in some way. They are finite in one way or another. A major cause of finitude of course, is being born. One’s (merely possible or actual — but from now on I will assume ‘actual’ unless otherwise noted) entry into a (merely possible or actual — but see the previous parenthesis) world results in their getting plunged into a world which has them as one center (among countless others, not totally unlike Nicholas of Cusa’s description of space as infinite and having infinite centers) and a horizon that extends only so far. One exists in the thick of a mileau with which they must constantly cope. A certain portion of the actual world gets exposed, or unconcealed (I try to define “exposure” below) to one, starting at birth and continuing through one’s lifetime. That is to say, one acquires and has available to them information. I will be leaving the term “information” undefined, except to accept Dretske’s claim that information can be either conceptual (information grasped intellectually or in terms of categories) or non-conceptual (information not grasped intellectually, for example information felt, as Nelson Goodman put it in his LANGUAGES OF ART, in the bones and in the muscles). I use the term “exposure” partly to avoid the implication that what I am talking about is necessarily conceptual in character. It is thoroughly obvious that any being that is not omniscient will have only a limited portion of the actual world exposed to them. Like being born, not being omniscient is a major cause of finitude.

Caravaggio’s painting THE CARDSHARPS very nicely illustrates, I think, four typical features of situations. First the boundaries of the information that is available to one form the boundaries of a situation. Second, to be in a situation is to be placed in the thick of things: one is grappling with the exigencies of a situation. Third, the information might be information grasped not by the mind but felt by the bones and muscles, emotionally. Fourth, there can be a conduit of information from one situation to another.

Caravaggio,, THE CARDSHARPS
 

Caravaggio’s painting depicts three situations. One situation comprises the situation of the callow young man, apparently of some wealth and status and vulnerable to being considered as a mark, who is pondering his cards. Exposed to him are one side of the cards, the table, and the front of the worldly-wise teenage cardsharp. Although he is directly looking at just the cards at the moment, I think it is safe to assume that in the very recent past he has acquired information about and has available to him information about the teenager and about the middle-age-ish man behind him. The young man, the mark, is a center of a situation within which a certain amount is exposed and from which much is hidden. The cards nicely serve as a visual symbol of the fact that his situation has boundaries shaped by a perspective and a point of view.

The teenage cardsharp of course has his own perspective, his own point of view, on the scene. What he is exposed to includes the back of the mark’s cards, the table, the cards he feels with his hands as he draws them from his back, the knife’s-edge tension he feels arising from the fact he has to accomplish his move perfectly, the feeling of danger arising from the fact the scene could very easily explode into violence — fists or swords — if he is not smooth enough. His own vulnerability, the fragility of his enterprise and its danger he cognizes in the bones and the muscles. Included in his situation is a kind of very broad present perfect. He has been shaped by a larger world which — if I remember my European economic history correctly — that has been suffering from harder times for a while now; and this card game is where he is now. All of this is his situation.

Oh, and yes — I almost forgot — part of the cardsharp’s situation includes a view of his confederate signalling to him the content of the mark’s cards. The confederate is in the thick of his own situation and of course he feels the knifes’s edge tension and danger, the fragility of their endeavor and the not at all improbable chance it could go wrong. These aspects of his situation are exposed to him, just as they are to his younger confederate. This situation serves as a conduit of information linking the mark’s situation with the teenager’s.

If I may be permitted to foreshadow what belongs to another post, we have here the 3-place accessibility relation between situations Rstu, where s is the signaler’s situation, t the teenager’s situation — a situation that includes a view of the signalling — and u is the mark’s situation. But more of that later, in a different post.

Any key or potential description that opens up a possible world maps to a situation. The key description ‘the walls of my apartment are fuchsia’ opens up, along with the phrase ‘and everything else is the same as in the actual world’ for me that possible world. The key description maps to the key situation that is part of this possible world, namely, the situation in which the walls of my apartment are fuchsia. I will say that situations hold in a possible world, including the actual world. That the walls of my apartment are portobello mushroom is a situation that holds in that possible world which happens to be identical with the actual world.

A situation comprises one or more state of affairs that obtains or could obtain. I use “comprise” for its suggestion that a situation surrounds, encloses, includes the states of affairs. The situation of my apartment in the actual world, for example, comprises the states of affairs ‘my cat Tiger is sleeping at my feet’ and ‘the walls of my apartment are portobello mushroom’, both of which obtain. Each of these states of affairs can be splintered off to comprise a distinct situation by itself.

“Known” aka “exposed to” aka “unconcealed” counts as a key description. That part of the actual world which I actually know, i.e., actually have information about, am cognitively exposed to, comprises my comprehensive actual situation. Everything that Smith has information about, everything that Morgenstern has information about, everything that Elizarraraz has information about, everything that an omniscient being has information about, comprises the comprehensive actual situation of Smith, Morgenstern, Elizarraraz and the omniscient being respectively. I will dub situations carved out this way from a possible world (including and primarily the actual world, of course) “informational” or “epistemic situations”; henceforth I will be using “situation” to refer to epistemic situations only, unless otherwise noted. A sentient being exists in an informational situation; this being is in the thick of things which press upon them and with which they must cope. That situation is defined by the information that is available to this being.

My own informational situation, the situation I am in, includes everything I am familiar in my apartment, as well as the view of the courtyard outside. It includes my knowledge that Houston is in Texas, Seattle is in Washington state, and St. George and Salt Lake City are in Utah. It includes all my old haunts in downtown Chicago and in that city’s Rogers Park, Near West, and Pilsen neighborhoods. Taken together, all this knowledge, all this information — both knowledge that and in-the-bones-and-muscles knowledge, comprises, along with the objects the information is about, what I will call my comprehensive actual situation.

My comprehensive actual situation includes numerous sub-situations — my cat Tiger’s sitting on a mat, the doorbell’s ringing inside my apartment. I will say that one is in a comprehensive actual situation or sub-situation; sometimes I will say that a situation — especially a sub-situation — holds for one. Sometimes, to emphasize the fact that the things within one’s situation are, typically, things with which they must cope, I will say one is grappling with and in the thick of a situation.

A bit later, when I discuss ostensible objects, I will be dropping the word “actual” and talk only about my “comprehensive situation.”

Now anything which blocks information from me … distance, shells, the practical difficulties (including getting the needed funding) of searching for probably-mythical creatures … will create a space for a possible world epistemically accessible for me from the actual world in which I exist. All that is required for the generation of a possible world that is epistemically accessible for me from my location in the actual world is that what I posit to “fill in” these spaces (a peanut in either shell #1 or shell #2 or shell #3; a Bigfoot | alternatively an absence of a Bigfoot roaming the forests of western Washington state; the sea-glass green or Venetian red or goldenrod yellow or periwinkle blue color of my neighbor’s walls) not be ruled out by what I know about the actual world.

The range of information available to me is obviously limited. It does not include enough information to absolutely rule out the identity of w0 (Bigfoot is roaming the forests of western Washington state) with the actual world, nor the identity of w1 (no Bigfoot is roaming the forests of western Washington state) with the actual world. It will not include enough information to rule out the identity of any other possible world that is epistemically accessible for me from the actual world — for example, the possible world in which the peanut lies under shell #1, the possible world in which it lies under shell #2, or the possible world in which it lies under shell #3. Nor does my comprehensive actual situation tell us whether, for any given GPS point in the Amazon, a butterfly is flapping its wings there, and if one is, whether its wings are purple or chartreuse. Nor does it tell us whether the walls of my neighbor’s apartment are colored sea-glass (viridian) green or Venetian red, a brick wall blocking this information from me, and my not having any other source of information that would tell me what the color is.

So unlike a possible world (including the actual world) which is “dense” in the sense that it answers every question, a situation has “holes” in it in the sense that it does not answer every question. It is littered with pockets of missing information. The situation comprises the actual world minus all the holes in which epistemically accessible possible worlds can be generated by any positing whose content does not rule out, given what I know about the actual world, its being a component of the that world. If a possible world is dense like a slab of most cheeses, a situation possesses many “holes” — pockets of missing information that can be filled in by positings consistent with what I know about the actual world — and is in that regard like a slab of Swiss cheese.

Or, to switch metaphors, my comprehensive actual situation is like a mesa (comprising all the knowledge/information I have) in southern Utah surrounded by a fog-covered plain. Lurking within within this fog are countless possible worlds that are epistemically accessible for me from my location on this mesa in the actual world.

Caspar David Friedrich, WANDERER. Okay — this isn’t Utah … but it’s close enough for government work

Since my comprehensive actual situation could be (in a sense of “could” that I will be clarifying shortly) identical with the Bigfoot possible world, or with the non-Bigfoot possible world, or with the ‘my neighbor’s walls are wine red’ possible world, and so on, my comprehensive actual situation could exist in more than one possible world. One is constantly finding out which possible world their comprehensive actual situation belongs to (and therefore which possible world the actual world belongs to). Is this the possible world the one in which the peanut is lying under shell #1 or the one in which shell #1 hides nothing except a piece of table top? Is this the world in which Bigfoot is roaming the forests of western Washington state, or the one in which no such creature is roaming those forests? Is this the world in which my neighbor’s walls are wine red, or the world in which they are some other color?

The key descriptions of these (epistemically accessible for me from my location in the actual world) possible worlds define circumscribed situations within those worlds. These descriptions might or might not be satisfied by the actual world. On the table in the Pilsen neighborhood of Chicago (that somber city) on which Elizarraraz has set up a shell game, the peanut may or may not be under shell #1. In the forests of western Washington state, Bigfoot might or might not be roaming. I will call these situations “derived from epistemically accessible possible worlds situations”, or “epistemic situations”. These are situations which the various epistemically accessible possible worlds that lurk in the holes in the swiss cheese, or in the fog surrounding the mesa, comprise.

Truth And Possibility

Epistemic Possibility. If I know nothing that rules out the identity with the actual world of the possible world which has as its key description ‘the peanut is under shell #1’, there is one possible world epistemically accessible for me from my location in the actual world in which the peanut is under shell #1. It is therefore possible — epistemically possible — that the peanut is under shell #1. That the peanut is under shell #1 is a possibility. As part of the possible world that has this as its key description, the peanut’s being under shell #1 could be a situation that is part of the actual world and therefore could become part of my comprehensive exposed actual situation. It’s being so, if I may be permitted to risk wearing out the word, is a definite possibility. Possibility defined in terms of what I do not know — my ignorance. This is the sense of “could” that is operative when, before the shell is turned over, I can truthfully and non-misleadingly say that the peanut could be under the shell, but then can no longer truthfully say this once the shell is turned over and turns out to be hiding nothing but empty air and a patch of table surface. This is a sense of “possible” that requires ignorance, not knowing. [See P.Z. Myers.] I will call possibility understood this way “epistemic possibility”.

Given my knowledge that the peanut lurks underneath one of the shells and that Elizarraraz would not do anything funny to manipulate the odds, there is a probability of 1 in 3 that the shell I select hides the peanut. Say I select shell #1. The credence I can assign to there being a peanut there is 1 in 3. This is the measure of the credence I can give to ‘this shell’ (say shell #1) ‘hides the peanut’. Once I overturn the shell to expose the peanut | a small expanse of tabletop the credence that there is a peanut there | nothing there becomes 1. Before that, when I observed just a shell, the credence to assign to there being a shell there is 1. Likewise, when I first observed the color of my apartment walls, the credence to assign to that color’s being portobello mushroom is also 1. This credence, or “probability”, is assigned relative to a body of knowledge that includes such propositions as those expressed by “I am not dreaming at the moment” and “I am not hallucinating at the moment”. I might be wrong about what propositions are to be included in this reference body of knowledge — for example, notoriously, I might believe that I am awake when in fact I am dreaming — but we should not automatically assume that having a false belief about what is included in my body of knowledge means that I do not know that thing. Also, I might not necessarily be able to express in a natural language (or in a formal language, for that matter) a proposition that is in fact part of my body of knowledge. [[[Present pluperfect]]]

Let me say, then, that a state of affairs is exposed, or unconcealed (I will use the two terms interchangeably; I will be using “unconcealed” when I am in a more Heideggerian mood), in a situation when, given the body of knowledge possessed by the sentient being whose situation it is, the credence to be assigned to that state of affairs is 1. When that credence is less than 1, that state of affairs counts as hidden or concealed.

Since my comprehensive actual situation is that part of the actual world that is exposed for me, every state of affairs in it is an exposed state of affairs. If a state of affairs is hidden, it is not part of my comprehensive actual situation.

Epistemic Truth: Correspondence is the truth-making factor, whether the state of affairs lies within a possible world or within a situation. But a sentence can correspond to a state of affairs with in a situation only if that state of affairs has been exposed within that situation: a situation comprises exposed states of affairs only. So when I utter a sentence that is true because it corresponds to a state of affairs within my situation, for example:

The walls of my apartment are portobello mushroom

it corresponds to an exposed state of affairs. All sentences that are true because they correspond to a state of affairs in my situation will be corresponding to an exposed, an unconcealed state of affairs.

Let me say that a sentence is true in a situation when it corresponds to a state of affairs within that situation. (For the best defense of the correspondence theory of truth that I have seen so far, see Joshua Rasmussen, Defending The Correspondence Theory Of Truth, Cambridge, Cambridge University Press, 2014). Let me also say that a situation makes the sentence true when a state of affairs within that situation corresponds to that sentence. Since a state of affairs is not comprised by a situation unless it is exposed within that situation, exposure, unconcealment, is a necessary condition for a situation’s making the sentence true. A situation cannot make true a sentence that corresponds to a hidden state of affairs, since that state of affairs cannot count as within or being a part of, that situation.

So if any of the following sentences is true, my comprehensive actual situation does not make them so. The states of affairs that would make them true are states of affairs in different situations.

1) The butterfly fluttering about in the Amazon at GPS point xyz has chartreuse wings

2) Shell #1 is hiding the peanut

3) The walls of my neighbor’s apartment are wine red

4) Bigfoot is roaming the forests of western Washington state

The first sentence, 1), might be generated by my laptop which I have programmed to spit out sentences of that form. Relative to my situation, it is an epistemic possibility: the situation that comprises that state of affairs could be drawn from a possible world whose identify with the actual world cannot be ruled out by anything in my body of knowledge. The number of variants of this situation is humongous, so the credence/probability to be assigned to 1) is extremely low. The probability to be assigned to 2) is 1/2. The credence to be assigned to 3 is 1 divided by the number of paint colors out there. My own Bayesian priors for 4) is about 1 in 100. (I know, I know — I have just lost any credibility any reasonable person might have been willing to grant me.)

Sentences 1 through 4 may or may not be made true by states of affairs exposed in other situations. For example, they may be made true by the comprehensive actual situation of an omniscient being to whom every state of affairs in the actual world is exposed, and for whom there are no brick walls, no funding difficulties blocking off the flow of information — a situation to which I will apply the label ‘worldly situation’. But none of them is made true by my comprehensive actual situation. Nor, as we will see, does my situation make true the sentences formed by prefixing “It is not the case that” to each one. The worldly situation does make at least one of A or ~A true in each case, so one would be justified in exclaiming “but surely A v ~A is true for each of these!” Yes — but it isn’t my comprehensive actual situation that makes them true.

Were however a conduit of some sort to link the situations relevant to 1 through 4 to my situation, either each sentence or its negation would be made true by my situation and in my situation. If my neighbor is reliable and he tells me that the walls of his apartment are wine red, he would have provided a conduit linking his comprehensive actual situation to mine and exposing in my situation the wine-red color of his walls. This state of affairs would then become part of my situation, having a probability of 1. [[[Need to discuss how something can fail to be a logical truth and still have a probability of 1.]]] Likewise, I might employ something like Google Earth to zoom in on that particular spot in the Amazon and discover there is indeed a butterfly with chartreuse wings fluttering about there. A sonar peanut detector might reveal to me that shell #1 is hiding the peanut, a conduit that perhaps is not quite totally kosher, like the one depicted in Caravaggio’s CARDSHARPS.

And a cryptozoologist with impeccable credentials might inform me that she was able to ascertain beyond a shadow of a doubt that the Bigfoot-like creature gallivanting around the various campsites in western Washington state impishly waving hello to campers and clearly enjoying their reaction, really is Bigfoot and not, as I had at first assumed it would have to be, my DFH friend Shaggy.

In each of these cases, an epistemic possibility — the ‘could’ generated by my ignorance — gets converted to an exposed actuality. Something that has an location in space-time gets unconcealed. Something gets made true in my situation by the exposure of a previously hidden state of affairs in a different situation. A probability of less-than-one gets turned into a probability of 1. To get exposed or to have been exposed is to have a probability of 1, where that probability is relative to one’s body of knowledge.

Knowledge has as one necessary component truth. I do not know that p unless p is true. Epistemic truth would reverse this relationship; p is not true in a situation (made true in that situation) unless p is known, exposed unconcealed — unless information, conceptual or non-conceptual, is available about it.

Here then, is the main take-away from this section: a situation cannot make true a sentence that corresponds to a hidden state of affairs. As a complete possible world, the actual world has sufficient resources, so to speak, to make true any sentence that corresponds to any state of affairs, hidden or exposed, within that world. But a situation does not have these resources. It is unable to expose every truth, and no sentence is true in a situation unless it has been exposed. Just as one does not go to Judge Judy to expose the truth in the murder trial of the century, I do not use my (current) comprehensive actual situation to expose the truth regarding whether there is a butterfly fluttering about at GPS location xyz in the Amazon, and, if so, what color its wings are.

Judge Judy trying to expose the truth of the Amazonian Chartreuse Butterfly Sentence

So much for truth. Let me turn now to compatibility/incompatibility. I will then combine these two separate discussion streams into a discussion of the truth condition for negation that will leave room for relevant implication.

Compatibility/Incompatibility

Compatibility and Incompatibility are binary relations holding between situations. I discuss these relations as they hold between situations drawn from spawned-from-the-unknown possible worlds and spawned from the known possible worlds respectively. I give a nod to the concept of defeasibility.

Situations Drawn From Spawned-From-The-Unknown Possible Worlds: The possible world in which the walls of my neighbor’s apartment are Venetian red is epistemically accessible to me because nothing in my body of knowledge rules out the identity with the actual world of this possible world. This possible world has “my neighbor’s walls are Venetian red” as its key description. The hand-wave “and everything else is the same as in the actual world” accomplishes the rest of this definition of the possible world. This world could (epistemic “could”) be identical with the actual world, and, upon the exposure to me of my neighbor’s walls as in fact being Venetian red, that particular situation (a singleton comprising just one state of affairs) drawn from this possible world would become part of my comprehensive actual situation.

Epistemic Compatibility: When a key-description situation s1 is drawn this way from a possible world that is epistemically accessible for me from my location in the actual world (remember, I will sometimes refer to these simply as “epistemically possible worlds” to save breath) and would therefore become part of my comprehensive actual situation s0 upon exposure, I will say that s1 is epistemically compatible with s0. Every situation s1 defined this way will be epistemically compatible with s0; this manner of definition provides a sufficient condition for epistemic compatibility.

So the key descriptions of all the epistemically accessible possible worlds lurking within the fog surrounding the mesa, all those ghost-worlds haunting all those holes in the lump of swiss cheese … all of these key descriptions define situations that are epistemically compatible with my comprehensive actual situation. No epistemically possible world will have a situation-defining key description that is incompatible with my comprehensive actual situation.

If I may be allowed to go out on a limb for a moment, compatibility is to be analyzed in terms of possibility, which in turn is to be analyzed in terms of possible worlds. As I will show shortly, different accessibility relations will allow some pairs of compatible situations and disallow others.

[[[A little reflection will show that every situation mapping to a key description of a possible world that is epistemically accessible for me from my location in the actual world will be epistemically compatible with my comprehensive actual situation. For any given key description, were there anything in my body of information and knowledge that ruled out its being part of the actual world, it would not be a key description for a possible world that is epistemically accessible for me. It therefore would not map to — really, be — a situation within an epistemically accessible world. It is not the case that it could be a part of the actual world; a fortiori, it is not the case that it is could be part of the actual world known to me or about which I have information. That is to say, it is not the case that it could be part of my comprehensive actual situation. Therefore all epistemic situations [define these above] are epistemically compatible with my comprehensive actual situation.]]]

Two situations can be epistemically compatible but incompatible in other ways. It is not completely inconceivable that, were I completely omniscient, or at least close to it, I might discover that the following two situations are nomically incompatible: the walls of my apartment are portobello mushroom, and the walls of my neighbor’s apartment are primrose pink. For suppose the universe is deterministic, at least on the post-quantum level. An incredibly complicated chain of events starting from the big bang, knowable only by an omniscient being, has resulted in the color of my apartment being portobello mushroom. This situation holds in all possible worlds that are a) nomically accessible from this world — i.e., the same laws of physics hold as in this actual world; and b) have the same initial conditions. Conceivably, there is just one such world, the actual world.

Another incredibly complicated chain of events starting from the big bang with the same initial conditions, also knowable only by an omniscient being, has resulted in my neighbor’s walls being chicory-flower blue (a beautifully paled even somewhat chalky ultramarine with a hint perhaps of violet). This situation also holds in all possible worlds nomically accessible from this world which have the same initial conditions. There might be just one such world, but it would still be true that in all possible worlds accessible from the actual world in the way described my walls are portobello mushroom and my neighbor’s walls are chicory-flower blue.

Necessarily, then, (nomically-plus-initial conditions necessary), my neighbors’ walls cannot be primrose pink at the same time my walls are portobello mushroom. The two situations preclude one another. They are incompatible.

To talk about two situations existing in the binary relation ‘incompatible’ is to talk about their necessarily not holding at the same time in the same possible world. In one sense or another of “cannot”, they cannot hold at the same time in the same possible world. Here the sense of the modal “cannot” is nomic-and-initial-conditions necessity. There is no possible world accessed this way from the actual world in which my walls are portobello mushroom and my neighbor’s walls are primrose pink.

Which sense of “cannot” is in play, which situations get included in the incompatibility relation will depend upon which accessibility relation one chooses. ‘Portobello mushroom in my apartment’ precludes and is incompatible with ‘primrose pink next door’ if the accessibility relation is ‘nomic and same initial conditions’, but not if the accessibility relation is ‘nothing in my body of knowledge rules out the identity with the actual world of the possible world in which my walls are portobello mushroom and my neighbor’s walls are primrose pink’. Because I am definitely not omniscient, my knowledge being limited and my ignorance vast, the two situations remain epistemically compatible. The latter epistemic accessibility relation renders the two situations compatible — epistemically compatible.

The situation described above whose corresponding description forms the key description for the rogue peanut world is not epistemically compatible with my comprehensive actual situation or with any of its sub-situations. For that situation would have to be part of the actual world; yet in the actual world peanuts do not jump around from shell to shell and never end up on the nose of the Mona Lisa. This is true of any world for which this is the key description: for example, the world in which Elizarraraz has painted the exterior of the building he owns goldenrod yellow instead of its very bright viridian green but the peanuts in his shell games went rogue; or the possible world in which the peanuts have also gone rogue but the sunflower in front is ever so slightly to the left … and so on ad infinitum. If I may be permitted a slight leap, then, I will assert that in all possible worlds in which peanuts have gone rogue, the key situation is epistemically incompatible with my comprehensive actual situation or any of its sub-situations. My situation (and each of its sub-situations) precludes any of the key situations, which means that never in any world shall the twain hold together at the same time.

Looking at situations drawn from spawned-from-the-known possible worlds will illuminate two dimensions of the epistemic incompatibility relation: the idea of difference, and the defeasibility of the aforementioned “cannot”.

Situations Drawn From Spawned-From-The-Known Possible Worlds: All the sub-situations within my comprehensive actual situation are, of course compatible with one another. That they are all holding at the same time is proof of their compatibility. Clearly, they do not preclude one another.

It will be worth keeping in mind (if only for the sake of clarity) that among these compatible situations are singleton situations mapping to a set comprising the same objects. For example, the situation that maps to the state of affairs named by ‘Tiger is sitting on my keyboard’ is clearly compatible with the numerically distinct situation named by ‘Tiger’s color is silver and the color of the Chromebook keyboard he is sitting on is Payne’s grey with a slight greenish undertone’. Clearly, ‘Tiger is sitting on my keyboard’ is compatible with ‘Tiger’s color is silver and the color of the Chromebook keyboard he is sitting on is Payne’s grey with a slight greenish undertone’

One would normally expect key situations defining spawned-from-the known possible worlds to be incompatible with the situation serving as its “raw material” so to speak if those two situations are taken to hold within the same possible world. If I access a possible world by taking the description “portobello mushroom walls” (the description for what I will call the “raw material situation”) and substituting for it the description “fuchsia walls”, the portobello mushroom wall situation and the fuchsia wall situations surely must be in different possible worlds. (Warning — this “must” is about to be caveated to death.) I am not, after all, trying to land in the same possible world I started with! I am trying to imagine what the effect would be if the color of the walls were different from what they are now.

And my walls — at least not in the same expanses — cannot be fuchsia and portobello mushroom at the same time in the same possible world. This I am willing to bet my paint brushes on. Unable to hold at the same time in the actual world — or in any other possible world — the two situations are incompatible. The one precludes the other from holding. If one holds in a possible world, the other cannot hold in that same world.

In positing a different possible world, one needs a feature, after all, that is, well, different from the raw material feature one is using. Without a difference in the key descriptions, one does not access a possible world different from the actual world. This leaves open the possibility that while one thinks there is a difference in key descriptions, there is in fact no difference.

What does count as a difference in the key descriptions? If we take color as our guide, we can, I think, confidently say that the fact my apartment walls are portobello mushroom means that the same expanse of wall cannot be fuchsia, periwinkle yellow, cornflower blue, or any other color at the same time it is portobello mushroom. The sub-situation within my comprehensive actual situation that is defined by ‘my walls are portobello mushroom’ cannot be identical with any situation defined by ‘my walls are x‘, where for x one can substitute any color name except “portobello mushroom”. Again, I am willing to bet my paint brushes on this. I mean, I certainly have never seen any wall that is both (in the same expanse) portobello mushroom and some other color. Nor can I imagine this. I will go so far as to say I cannot conceive this — not in this actual world nor in any other possible world. Necessarily, a wall cannot be portobello mushroom and some other color at the same time and in the same expanse.

But why should one think this? Knowing that two situations hold at the same time in the actual world if dispositive for their being compatible. But what is dispositive for the incompatibility of two situations within the same possible world? Look as hard as I may in the actual world for a wall that is both fuchsia and portobello mushroom in the same expanses at the same time, I will surely never find one. But isn’t a search like this a bit like searching for an elephant-sized swan? I may never find one — but that is not an absolute guarantee I never will! As Tom Kyte, the database guru likes to remark, you can’t prove a negative such as “no swans the size of an elephant exist”.

Certainly I am unable to imagine a wall that is both of the aforementioned colors at the same time. It would seem, then that I cannot conceive of these two situations holding at the same time in the actual world, right?. (Spoiler alert: no.) And isn’t the inability even to conceive this co-holding evidence that the concept of their compatibility is incoherent?

It is also true, however, that I cannot imagine a mass being at the same time a wave. Yet on my layman’s Wikipedia-level understanding of physics, every mass is also a wave. The situation to which corresponds the description “lumbering mass furiously scribbling away on a Chromebook” exists at the same time as the situation corresponds to the description “tiny petite wave furiously scribbling away (more precisely, keyboarding away) on a Chromebook”. So the two situations must be compatible. How can that be?

The apparent incompatibility can be resolved, I think, if we heed Leibniz when he tells us that imagining is not necessarily conceiving. I cannot really imagine a icosahedron with its 20 equal faces. But I can conceive of one. I suggest, then, that while one may not be able to imagine the situations “lumbering mass” and “tiny petite wave” holding for the same entity at the same time, one may be able to conceive this.

Certainly I cannot conceive this — my conceptual resources are too limited. But I am willing to bet that the physicist, as they delve into the properties of this mass in an ever-more sophisticated way, will end up ascribing properties to this mass that are also properties of a wave. For all I know, I have wave-properties such that, were the wave (per impossibile) long enough, I would be able to pass through two separated doors at the same time, just as, if I am not mistaken, an electron is able to pass through two separated slits at the same time. Let us suppose that there is a long series of mathematical equations that describe this; and let’s call this description a “conception of a lumbering mass that is identical with a tiny petite wave”. This description would correspond to a single situation — a mass that is identical with a wave. Given enough knowledge, the description ‘mass’ merges into the description ‘wave’; and the situation named by ‘is a mass’ is identical with the situation named by ‘is a wave’. The identity of the “two” situations is, of course, a sufficient condition for their compatibility.

Let me pause for a moment and elucidate a couple of matters, just for the sake of clarity. First, identity is a two place relation, with one singleton situation bearing one name related to the same singleton situation bearing a different name. The “two” situations are numerically one, comprising the same proposition aka state of affairs at t. Other propositions/states of affairs might comprise the same objects, but be comprised by different situations. The same lumbering mass/petite tiny wave may be part of the state of affairs named by ‘lives in Houston’ and also part of a different state affairs named by ‘studied philosophy in Chicago at Loyola University’, with the result that it is involved in three numerically distinct situations each comprising a different state of affairs.

I continue. I have never encountered a wall that is both fuchsia and portobello mushroom in the same expanse and at the same time — just as I have never encountered a large mass that in any obvious way is also a wave. I am unable to picture imaginatively a wall that is both colors at hte same time — just as I am unable (at present) to picture imaginatively a large mass that is also a wave. I am lacking a non-pictorial conception of a wall that is both colors (henceforth “at the same time and in the same expanse” will be understood) — and until I have such a conception, I will continue to regard the two wall-color situations as incompatible. In no possible world in which walls (or anything for that matter) have colors are the walls of my apartment both fuchsia and portobello mushroom. As parts of states-of-affairs-comprised-by-situations-that-are-parts-of-possible-worlds these two situations must be parts of possible worlds. To put the matter a bit more simply, the walls cannot be these colors without being in different possible worlds. I am in the same position with regard to the wall colors as one would have been with regard to mass/wave situations before our knowledge of physics expanded enough to give us a conception of the fact that a lumbering mass is also a wave.

For all I know, we may eventually broaden our knowledge enough to allow us to conceive an identity in the same possible world of the fuchsia wall situation and the portobello mushroom situation. Or maybe an infinite or at least extremely large intelligence already has such a conception. I am not willing to bet my paint brushes, however, on anyone arriving at such a conception in my lifetime, or ever. Nor am I able to ground the assertion that this conception will never arrive, no more than I can ground the assertion that we will never discover an elephant-sized swan. Someone in 1801 might have made the same assertion regarding large masses and tiny waves. All I can say is “so far as I know, the same expanse of wall cannot be, in the same world, at the same time, and in the same expanse both fuchsia and portobello mushroom.

In other words, there is nothing in my body of knowledge that would rule out the hypothesis that, among all the possible worlds in which a wall can be some color and in which what it is to be a color (however that may be articulated) is the same as it is in the actual world, there is no world in which the same expanse of wall is both fuchsia and portobello mushroom at the same time. So far as I know there is no possible world in which ‘fuchsia-wall’ and ‘portobello-mushroom wall’ are two names for the identical situation. The necessity, and therefore the incompatibility, are epistemic, grounded in my lack of knowledge, my ignorance. The necessity and the incompatibility are defeasible.

Side note for the sake of clarity: I have moved, then, from discussing individual worlds that are epistemically accessible for a sentient being S (the possible world in which Bigfoot does indeed roam the forests of western Washington state; the possible world in which the walls of my neighbor on the other side of the brick wall I am facing as I write this are wine-red) to sets of possible worlds that ground epistemic necessity (there is nothing in my body of knowledge that would rule out the hypothesis that, in the set of possible worlds that are accessible in such and such a way from the actual world, none comprise situation s).

Strictly speaking, epistemic necessity is compatible with, does not preclude epistemic contingency (there is nothing in my body of knowledge that would rule out the hypothesis that, in the set of possible worlds that are accessible in such and such a way from the actual world, there is at least one that comprises situation s). This is perhaps a bit like saying “all unicorns (all zero of them) are yellow ocher” and “all unicorns (all zero of them) are rainbow-colored”, where the particular set of rainbow colors in question excludes yellow ocher. Unlike the usual uses of “necessary” and “possible” “epistemic necessity” cannot be defined as “not epistemically possible” and vice versa.

Nonetheless I do think there is a certain asymmetry between epistemic necessity and epistemic contingency. Reviewing possible worlds to try to find one in which the walls in it are (at the same time and in the same expanses) both fuchsia and portobello mushroom is rather pointless given that one does not know what it means for a wall to be both these colors at once. And one does not know what this means because one does not have access to the truth conditions for “this wall is fuchsia and portobello mushroom at the same time”. (Henceforth I will call this the the “fuchsia/portobello mushroom wall sentence”.) Currently, one lacks the means for getting these truth conditions. Imagination would have been one means. My imagining Tiger sitting on my Navajo mat suffices to give me the truth conditions for the English sentence “Tiger is sitting on my Navajo mat”. I know the meaning of that English sentence because, via the imagination, I know what would be the case if the sentence were true. But imagination certainly does not give me a way to get at the (quite possibly non-existent) truth conditions for the fuchsia/portobello mushroom wall sentence. My imagination can fail me in giving me the truth conditions for the English sentence “this humongous lumbering mass is also a tiny petite wave”, but someone (I am confident) has a conception stated in the mathematical language of physics of precisely this. (Maybe, in honor of Hilary Putnam’s division of semantic labor which relegates to certain experts the distinction between a beech and an elm, I will ask a physics undergraduate to write this down for me.) But no such mathematically-expressed conception seems to exist to give us the truth conditions for the fuchsia/portobello mushroom wall sentence. That is to say, so far as I know no such conception exists.

At the time of this writing, I can state confidently that I do not have a conception for the fuchsia/portobello mushroom wall situation that would give me access to the truth conditions for the fuchsia/portobello mushroom wall sentence. I also lack a conception for the humongous lumbering mass/petite tiny wave sentence (I will need to make sure above that I have named this sentence). But I am fairly confident that I can appeal to someone in my linguistic community (some physics undergraduate, for example) who does have a conception ghat gives them access to the relevant truth conditions, just as Hilary Putnam in his MEANING OF MEANING can appeal to a tree expert for the truth conditions of ‘is an elm’ versus ‘is a beech’ even though he lacks access to those truth conditions by himself. The access is distributed across members of a linguistic community unlike epistemic accessibility, which — at least given how the concept has been defined so far — is restricted to individual sentient beings. Let me define, then, what I will call semantic accessibility in the following way:

A world w0 is semantically accessible from w for an speaker S (in w) in linguistic community L to which S belongs iff S is able to consult with speakers in the linguistic community L to which S belongs who have a conception giving them access to the truth conditions of the key description of w0.

Then, p is semantically necessary (for S in L in w) iff p is true in all possible worlds that are semantically accessible from w (for S in L in w). And p is semantically possible (for S in L in w) iff p is true in at least one possible world that is semantically accessible from w (for S in L in w).

I am call this accessibility relation “semantic” of course because it is concerned with truth conditions. A “conception” that gives one access to a particular set of truth conditions is whatever resources one possesses that lets one know what it would be for the sentence “snow is white” to be true (namely, that snow is white). Since semantics is concerned with language — the meanings of words — and language is a communal enterprise, it is natural that the definition of semantic accessibility should include a reference to a linguistic community.

I started my discussion of possible worlds by asserting them to be identical with sets of descriptions, some of which are satisfied by states of affairs in the actual world (a “brick”, to speak metaphorically), and others which are left unsatisfied (a “written description” is in place where the brick should be). Without access to the truth conditions of a description, one has no access to what the description means. One therefore has no access to the possible world the key description is meant to open up. If, say, an omniscient mind knows the truth conditions, that mind has access to that possible world. For us more limited creatures, however, we may not necessarily know if there is a possible world out there we can ever hope to gain access to in the first place. As time goes on and — as in the case of humongous lumbering masses/tiny petite waves worlds — we may gain a conception which gives us access to the world and opens it up to us. I can no more definitively say this won’t happen for the fuchsia/portobello mushroom wall world any more than I can say that I will never encounter an elephant-sized swan. I am willing to bet that the communal body of knowledge — the resources available to members of the linguistic community to form the needed conception — will never expand so as enable anyone to access the truth conditions for the fuchsia/portobello world, but….

So we can divide worlds — the sets of descriptions, satisfied or unsatisfied, real or merely purported [[expand on this — difference between nonsense such as “trd4r3e3bbubijvbhjihyiurhtrg” and words that are intended to be used to describe but fail in that function because the truth conditions are lacking) into those worlds regarding which there is nothing in the communal body of knowledge that would rule out (preclude) their belonging to the set of possible worlds, i.e., the set of worlds, that is to say, the set of descriptions whose truth conditions one has access to. If a world is not a possible world, it is an impossible world, a status that it may (epistemic “may”) or may not have permanently.

[[[Let me note parenthetically that the entities I have defined with reference to a personal or communal body of knowledge — epistemically accessible possible worlds, epistemic probability, semantically accessible possible worlds rather paradoxically depend for their definition precisely on what is not in the body of knowledge. For probability part of the relevant body of knowledge consists in knowing what one doesn’t know — I don’t know under which shell the peanut lies, though I know that there is one peanut and that it lies under one of the shells.]]]

[[[Explain this a bit more. Compare with probability as a number relative to a body of knowledge.]]]

To continue: I propose, then that every key situation to which corresponds a key description generating a spawned-from-the-known possible world be regarded at first as (epistemically) incompatible with the situation in the actual world that formed the raw material of this key description. As far as one knows — that is to say, unless and until one’s body of knowledge has expanded sufficiently — the possible situation has to be seen as belonging to a possible world different from the actual world and as numerically distinct from the situation that forms its raw material.

Epistemic incompatibility, then, is the converse of epistemic accessibility. A possible world is epistemically accessible for me from my location in the actual world if there is nothing in my body of knowledge that would rule out its identity with the actual world; and a situation within that possible world could (epistemic “could”) be part of the actual world. For example, there is nothing in my body of knowledge that would rule out the identity with the actual world of the possible world in which my neighbor’s walls are wine red; and the situation named by ‘my neighbor’s walls are wine red’ could be a situation within the actual world. Correlatively, there is nothing in my body of knowledge that would give me the conceptual resources to conceive of my neighbor’s walls being both wine red and sea glass green in the same possible world; or of my own walls as being both fuchsia and portobello mushroom in the same actual world; or any wall in any possible world in which there are things called “walls” that have colors having two distinct colors at the same time and in the same expanses. There is nothing in my body of knowledge that would rule out the non-identity with the actual world of the possible world in which my apartment walls are of a different color. More generally:

A world w0 is epistemically distinct from w for an agent S (in w) iff there is nothing in S‘s body of knowledge that would rule out the hypothesis that w0 != w.

And:

A key description d0 is epistemically incompatible with a key description d for an agent S in world w for whose definition d is key iff every world w0 accessible for S by way of a key description d0 is epistemically distinct from w.

[[[[Two descriptions d0 and d1 are epistemically incompatible for an agent S (in w) iff, given the body of knowledge possessed by S, d0 and d1 together fail to provide a key description giving S access to a possible world.]]]]]

And:

Two situations s and s0 are epistemically incompatible iff the key descriptions to which they correspond are epistemically incompatible.

That two situations are incompatible is defeasible. [[Need a similar definition of compatibility.]]

To sum up this discussion of epistemic compatibility/incompatibility: Key description situations drawn from spawned-from-the-unknown possible worlds are epistemically compatible with the corresponding situation in the actual world when they are epistemically accessible from the actual world. Otherwise they are incompatible. Key description situations drawn from spawned-from-the-known possible worlds may at first be assumed to be epistemically incompatible with their “raw material” situations in the exposed part of the actual world, but then may become epistemically compatible as our knowledge grows. I dare say, however, that it is rarely — if ever — the case that one should bet the ranch — much less one’s paint brushes — on the incompatibility between two situations ever morphing into compatibility.

[[[[Lumberoom: Imagination, then is not an absolutely reliable guide to incompatibility. The mere inability to imagine two situations as being the same situation is not exactly an absolutely reliable guide to their being incompatible and therefore forever doomed to non-identity. My mere inability to imagine that the walls of my apartment, in the same expanses, are at once fuchsia and portobello mushroom does not suffice to guarantee that they cannot be. At the same time, I do not know what it would be for the walls (in the same expanses — henceforth this will be understood) of my apartment to be both portobello mushroom and fuchsia at the same time. I do not know — I haven’t the faintest idea — what would be the case if the sentence “the walls of my apartment are both fuchsia and portobello mushroom at the same time” were true. The truth conditions for that sentence are lacking for me — I don’t have access to these truth conditions. I am therefore unable to posit a possible world which has this sentence as its key description.]]]]

[[[[But I do have access to the truth condition for the possible world in which the walls of my apartment are fuchsia, not portobello mushroom. I know what would be the case if the sentence “the walls of my apartment are fuchsia” were true. I have the knowledge expressed by the sentence “this is fuchsia” and the knowledge of what it is to paint walls a certain color and whatever other knowledge is required to give me the conceptual resources to know this truth condition. I am therefore able to posit the fuchsia apartment wall possible world.

At one time, no one would have had the conceptual resources to know the truth conditions for the possible worlds (one of which which happens to be the actual world) in which “lumbering mass at work on its laptop scribbling away” is describes the same situation as does “petite tiny wave at work on its laptop scribbling away”. I am not sure I have the conceptual resources to know these truth conditions. I am confident, however, that a competent physicist would. Perhaps even they would not be able to imagine these truth conditions pictorially; but perhaps the ability to produce a series of equations describing the situation would count as knowing the truth conditions. At one point in time (t0) no sentient being S had the conceptual resources afforded by the needed body of knowledge; then at another point in time (t1) some agents do. At t0 the prudent thing to say would have been “so far as I know, ‘is a wave’ and ‘is a particle with mass’ are incompatible descriptions of the identical situation (namely, this person scribbling away)”; at t1 one can now say they are indeed compatible descriptions of the same situation.

Now, I submit, at the time of this writing, the prudent thing to say is that so far as I know, ‘the walls of my apartment are fuchsia” and “the walls of my apartment are portobello mushroom” are incompatible descriptions of the identical situation (namely, the walls of my apartment being such and such a color). But obviously I have no guarantee that my current body of knowledge and the resulting conceptual resources available to me will always be the same. Perhaps these can change just as they did in the case of the mass that is also a wave. The only entity that could provide such a guarantee would be an omniscient being. My being finite — i.e., my being situated — means that the ability to provide such a guarantee is likely to be forever beyond my reach. So I have to rest content with the “so far as I know”.

Let’s say, then, that incompatibility is relative to a body of knowledge, just as epistemic accessibility and probability (at least according to Kyburg) are. The incompatibility of descriptions d0 and d1 is relative to the body of knowledge possessed by a (possibly fictional) omniscient being who knows (if they do know this) that the two can never describe the same situation at the same time. The epistemic incompatibility of d0 and d1 is relative to a body of knowledge that fails to provide the resources — a failure that quite possibly will never be remediated — to give one access to the truth conditions for a single situation’s holding for which both d0 and d1 serve as key descriptions at the same time. [[[To have access to the truth conditions is to have access to a possible world.]]] This incompatibility means that d0 and d1 can never, together, provide a key description giving one access to a possible world. ]]]]]

[[[[[[

To gain access to a possible world is to have the ability, provided by one’s body of knowledge plus whatever other abilities, to conceive or represent the truth conditions of that world’s key description. If, given one’s body of knowledge and one’s cognitive abilities, one cannot cognize the truth conditions of the combination of d0 and d1, that combined description cannot open up or give one access to a possible world. The one description precludes the other. And there is no situation that they, in combination, correspond to. This absence of truth conditions is what provides the meaning of epistemic incompatibility.

Generally, one would expect that coming up with an ostensibly different key description (my walls are fuchsia, not portobello mushroom; Tiger is from planet XZDOIN#K deep in the Orion galaxy, not planet Earth) would result in pairs of incompatible descriptions and therefore incompatible situations which cannot hold at the same time in the same possible world (especially in the actual world). “Different” means “not identical”. Different description, different situation.

The one exception to different descriptions generating different situations would be when the descriptions are parts of a longer description whose individual sentences (perhaps in the forms of mathematical statements) cohere — maybe surprisingly –into a single description. The physicist starts with a mathematical description of a lumbering mass…and when they finish, end up with something that also describes a very small wave. They may still be unable to picture something’s being both a lumbering mass and a tiny petite wave at the same time — nonetheless, their long mathematical description constitutes a setting forth of the truth conditions. ]]]]]

[[[Need now to show how room is left for a situation not to be compatible with itself]]]

I now join these two streams: the discussion of truth, and the discussion of compatibility/incompatibility.

Non-Bivalent And Inconsistent Situations

Non-Bivalent Situations: The binary relation ‘compatibility’ holding between two situations gives us a truth condition for negation that will let us see how situations can be both bivalent and inconsistent. The case for bivalent situations is perhaps a bit less … venturesome … than the case for inconsistency. We will see where I end up. Let’s take a look at this truth condition for negation, but modified so as to be talking about epistemic compatibility, not compatibility per se.

A situation makes ~A true if and only if every situation [epistemically] compatible with it fails to make A true.

RL, p. 75

Making A True: Above, we have seen that a situation makes A true when that situation contains a state of affairs to which A corresponds. But the situations we are concerned with, epistemic situations, contain only states of affairs that are exposed, that is to say, unconcealed. So a situation makes A true only when A corresponds to an exposed state of affairs within the situation.

Epistemic Compatibility: As we have seen, every sub-situation within my comprehensive actual situation is epistemically compatible with every other such sub-situation and with my comprehensive situation itself. The fact that all these sub-situations hold at the same time in the actual world ices their all being compatible. [[[Be sure to reconcile this with the impossible cube. The impossible cube can never be actual.]]] Drawn from the actual world, these sub-situations are also epistemically compatible with any other situation drawn form the actual world by virtue of the fact that the actual world is epistemically accessible from the actual world. For any key description that is used to define the actual world, there is nothing in my body of knowledge that would rule out, i.e., preclude its being a part of the actual world.

All these actual situations are compatible with one another by virtue of the fact that that all situations drawn from possible worlds (one of which is the actual world) that are epistemically accessible for me from my location in the actual world are epistemically compatible with my comprehensive actual situation. And as we have seen, all possible situations — not just those possible situations that happen also to be actual — that are drawn from epistemically accessible possible worlds are epistemically compatible with my comprehensive actual situation. [[[Make sure I am not committing some part/whole fallacy.]]]

Negation: Negation works unproblematically for the dense parts of the lump of swiss cheese, for the mesa surrounded by the fog, for that part of the actual world which is exposed to S. Let’s take, for example, ~A to be the sentence “It is not the case that the walls of my apartment are fuchsia.” My comprehensive actual situation makes that sentence true.

Now we have seen that a sub-situation is compatible with the situation of which it is a part. So every sub-situation within my comprehensive actual situation s0 is epistemically compatible with s0. For no sub-situation within my comprehensive actual situation makes A (“It is the case that the walls of my apartment are fuchsia”) true. One of these sub-situations is, of course, the singleton situation comprising the state of affairs at t identical with the proposition expressed by “the walls of my apartment are portobello mushroom”, namely A. That situation especially fails to make A true. Tiger trying to get onto the keyboard as I write this; the doorbell ringing, the chalky Venetian red color of the cliffs in Southern Utah — list them all — each is epistemically compatible with s0 and each fails to make A true.

And surely every situation outside my comprehensive actual situation will also fail to make A true. [[[Discuss situations outside s0.]]] For example, whatever the color of my neighbor’s apartment walls may be, that is not a singleton situation what will make it true that the color of my apartment walls are fuchsia. I think it is fairly safe to go out on a limb, then, and say that every situation epistemically compatible with s0 fails to make “it is the case that the walls of my apartment are fuchsia” true. s0 therefore makes the sentence “it is not the case that the walls of my apartment are fuchsia” true.

Note that if nomic-and-initial conditions compatibility were in play, my neighbor’s walls being periwinkle yellow, say would make it true that my walls are fuchsia if the initial conditions at the big bang deterministically led up to these two causal lines. But I think it would violate our sense of what ‘not’ means if my neighbor’s walls being wine red made “it is not the case that my walls are fuchsia” true. This is why I think “compatible” should be taken to mean “epistemically compatible” in the truth condition for negation.

Negation works unproblematically for the dense parts of the lump of swiss cheese, for the mesa surrounded by the fog, for that part of the actual world which is exposed to S. But matters are different inside the holes in the lump of swiss cheese, or down in the depths of the fog surrounding the mesa. Consider the sentence “the walls of my neighbor’s apartment are wine red”.

Consider the situation in the possible world, epistemically accessible for me from my location in the actual world, that has as its key description “the walls of my neighbor’s apartment are wine red”. Within this possible world, the key situation (a singleton) would, if the state of affairs it comprises obtained in the actual world, make the sentence “It is the case that the walls of my neighbor’s apartment are wine red” true. Let this sentence be A at the moment.

As part of a possible world that is epistemically accessible for me, this key situation counts as an epistemic situation. As a situation that is hidden from me, as being attached to a probability less than 1 (but presumably greater than 0), it is not part of my comprehensive actual situation, which comprises only exposed states of affairs with a credence of 1. But being an epistemic situation, it is epistemically compatible with my comprehensive actual situation.

A mere probability does not make a sentence true. The probability that the peanut is under shell #1 is 1/2, as is the probability that the peanut is not under shell #1. But this probability does not make either “The peanut is under shell #1” or “The peanut is absent from shell #1” true. The probability is not the truth-making factor. The assertion “the probability is 1/2” does not answer the question “what makes it true that the peanut is under | is absent from shell #1?” What answers that question is rather the peanut’s presence under | absence from shell #1.

Likewise, the probability that my neighbor’s walls are wine red is something like 1/the number of wall paint colors that are out there. Let’s say the probability is 1/10000. The assertion “The probability is 1/10000” is not the answer to the question “Are my neighbor’s walls wine red?” (Henceforth the “wine red question”.) The proper answer to that question would be “That my neighbor’s walls are wine red”. That the probability is 1/10000 gives one the possibility that my neighbor’s walls are wine red. But wine-red walls are what make the sentence true — if it is true — not the mere possibility of wine-red walls. The sentence “My neighbor’s walls are wine red” corresponds | fails to correspond to whatever state of affairs obtains as to the color of my neighbor’s walls, not to whatever state of affairs might obtain.

[[[To say that a sentence is “merely probable” is not yet to say that it is true, though of course it might also turn out to be true in the end. The mere probability that the peanut is under shell #1 is not a truth-maker.]]]

Every brick that composes this particular epistemically accessible possible world is present and is the same brick that composes the actual world, with the exception of one missing brick. In place of this brick is a piece of paper on which is written “The walls are wine red”. In order to be true, the wine-red sentence has to correspond, so to speak, to the brick, not to the inscription.

Nothing within my comprehensive actual situation makes the wine-red sentence true: not the portobello mushroom color of my walls, not Tiger’s sitting on the mat, not my doorbell’s ringing — no sub-situation in this situation comprising whatever states of affairs does. And as we have just seen, neither does the singleton situation that, outside my comprehensive actual situation, is part of the for-me epistemically accessible my-neighbor’s-walls-are-wine-red possible world. So according to the above truth condition for negation, it is false. A, that is to say, “It is the case that my neighbor’s walls are wine red” is false.

But if bivalence held for my comprehensive actual situation, [[[remember to distinguish between holding in and holding for a situatioun]]], then ~A would have to be true: “It is not the case that the walls of my neighbor’s apartment are wine red”. Then the following sentence would have to be true: “My neighbor’s walls are sea-glass green; or my neighbor’s walls are Navajo white; or my neighbor’s walls are goldenrod yellow; or my neighbor’s walls are Tiepolo pink; or my neighbor’s walls are cornflower blue; or my neighbor’s walls are ultramarine blue; or my neighbor’s walls are Venetian red….” and so on for every wall color except for wine-red.

But using the same reasoning as for wine red, each of these or’d sentences is false for my comprehensive actual situation. That is to say, no situation epistemically compatible with my comprehensive actual situation s0 — no sub-situation in or within s0, and no situation drawn from a possible world epistemically accessible for me from my location in the actual world — makes any of these or’d sentences true. So the entire sentence that comprises them is false. So for my comprehensive actual situation s0 and for all situations epistemically compatible with it, both “It is the case that my neighbor’s walls are wine red” and “It is not the case that my neighbor’s walls are wine red” are false.

Bivalence holds within an epistemic situation (i.e., states of affairs are exposed to a sentient being), in that way my comprehensive actual situation is like a possible world. But bivalence fails for my comprehensive actual situation i.e., when I reach outside that situation to consider situations that are hidden from one and sentences whose truth is merely probable. When considering the truth of A requires a reach into the fog surrounding the mesa, or into one of the holes in the lump of swiss cheese, both A and ~A are false. One’s comprehensive actual situation turns out to be not enough to render at least one of these sentences true. This in turn means that there exist situations for which, for certain sentences A (obviously not all), “If A then A” is false. In this way, Relevant Logic can avoid the Classical Logic paradox: “A –> (B v ~B)”, alternatively, “A –> (B –> B).

Complete, a possible world answers the wine-red question as well as the peanut question as well as the Bigfoot question as well as the Amazonian chartreuse butterfly question. Finite and fragmentary, a situation cannot. A situation is partial. Like Judge Judy’s courtroom being the wrong tribunal for answering the question who is the culprit in the murder of the century, a situation is the wrong tribunal for answering the wine-red and the peanut (is the peanut under shell #1 or under one of the other two shells?) questions.

Partial situations allowing for this can exist because situations are not complete. They do not answer every question. (Does a Bigfoot creature roam the woods of western Washington state or does it not? Is there a butterfly fluttering about in the Amazon at GPS location xyz or not; and if there is, are its wings chartreuse? Is the peanut under shell #1 or does that shell hide only a small expanse of table-top? Are the walls of my neighbor’s apartment wine red or some other color?) My comprehensive actual situation remains the same whichever happens to be the correct answer. The identity of this situation does not depend upon the answer. This sameness leaves room for non-bivalent situations. [[[[Expand on this]]]]

But as we saw above, the identity of a possible world does depend upon the answer. The Bigfoot possible world is not identical with the non-Bigfoot possible world. So possible worlds do not allow for the failure of bivalence. In any possible world, including the actual world, either a Bigfoot creature roams the woods of western Washington state or does it not. Unlike situations, which can be partial, a possible world must be complete. It must answer every question.

All of the above is my attempt to nail down, by putting in my own terms, Mares’ discussion of non-bivalent situations in his RELEVANT LOGIC: A Philosophical Interpretation. This is an exercise in writing to learn. In particular, this is my attempt to nail down the following passage from Mares:

Partiality is straightforward [ahem! Cough cough], so we will start with that. Consider the situation that consists of the information that is currently available to me. The includes what is going on in my study as I write this section of my book, and what I can see through my window. Nothing happening here makes it true that it is currently raining in Toronto (which is on the other side of the globe). But situations in which it is raining in Toronto are compatible with my current situation. So neither ‘It is raining in Toronto’ nor ‘It is not raining in Toronto’ is true in my current situation. Thus bivalence fails for this situation and the situation is partial.

RL, p. 75

Let me turn now to inconsistent situations.

Inconsistent Situations: Dealing with inconsistent situations is a bit more of a stretch. But let me venture (as I try to strengthen my shaking knees) the following attempt to use the concept of ostensible objects to allow for inconsistent situations. There are singleton situations, I claim, that are incompatible with themselves because they comprise impossible objects. ‘Compatible’ is not always a reflexive relation for a situation.

First, some words on the concept ‘incompatible’.

Compatibility Again: Situation s1 is compatible with situation s2 when s1 and s2 can hold at the same time. For example, the situation that corresponds to the description “Tiger is sitting on the mat” (where I have deposited him to keep him off my keyboard) holds at time t. The situation that corresponds to the description “The doorbell is also ringing in my apartment at t” also holds at t. [[[Need to say something about “corresponds” vs. “defines”]]] That the two situations hold at the same time clearly means they are compatible. Their co-holding is dispositive. And as two sub-situations within my comprehensive actual situation s0 (I will be reserving “s0” to name my comprehensive actual situation unless otherwise noted), one would of course expect them to be compatible, as are all sub-situations within s0.

In the actual world, my cat Tiger was born on earth and did not travel here from the planet XZDOIN#K deep within the Orion galaxy. But surely the situation whose description forms the key description of the possible world in which Tiger is from XZDOIN#K (with cats, those creatures of mystery, one always has one’s suspicions) is also compatible with the doorbell’s ringing and with many of the sub-situations within my comprehensive actual situation. Since this is a situation drawn from a spawned-from-the-known possible world, it is perhaps fairly safe — though as we have seen, not absolutely safe — to say that this situation is not compatible with the situation that formed its “raw material”, Tiger’s origins being the planet earth. Surely the situation defined by the situation “Tiger is from planet earth” cannot co-hold with the situation defined by “Tiger is from planet XZDOIN#K deep within the Orion galaxy”. The two situations are different. They cannot be identical situations. The two situations are not compatible. The one precludes the other.

However, the mere fact that two descriptions seem like they cannot be descriptions of one and the same situation does not mean that these two descriptions cannot correspond to the identical situation. What is more, one of the differing descriptions may be a key description of a spawned-from-the-known possible world and the other may be the “raw material” of this description. One may think they have accessed a possible world numerically distinct from the actual world, but end up landing in the same old actual world anyhow.

Above, I have said that two situations s and s0 are epistemically incompatible iff the key descriptions to which they correspond are epistemically incompatible. In turn, a key description d0 is epistemically incompatible with a key description d for an agent S in world w for whose definition d is key iff every world w0 accessible for S by way of a key description d0 is epistemically distinct from w. [[[[Two descriptions d0 and d1 are epistemically incompatible for an agent S (in w) iff, given the body of knowledge possessed by S, d0 and d1 together fail to provide a key description giving S epistemic access to a possible world.]]]]]

Ostensible Objects:

[[[This particular expanse of wall cannot be portobello mushroom or sea-glass green at once. The one situation precludes the other. The two situations are not compatible. And their inability to exist at the same time is dispositive for their being incompatible.

Likewise, the holding of two situations at the same time is dispositive for their being compatible, their not precluding one another. My cat Tiger’s being on the mat (where I have just deposited him to keep him from sitting on my keyboard) at the same time that the doorbell is ringing definitively shows that these two situations are compatible. ]]]

Now I will try to show that ‘compatible’ is not always a reflexive relation. A situation can be incompatible with itself. If a situation is incompatible with itself, it excludes itself. This is a funny position for a situation to be in, a bit like Mark Twain or Groucho Marx or whoever said he refuses to belong to any club whose standards are so low as to have him as a member. But there we are.

Take a look at a depiction of an impossible cube, inspired by the Dutch artist Maurits Cornelis Escher.

https://www.youtube.com/watch?v=UibfZnfNYyc

If you see the cube as if a bit from above, take a look at the vertical bar closest to you, and the bar that gets experienced as running horizontally behind that bar to connect to two lower vertices behind it. Were this an actual object existing in the physical world and you were requested to touch the horizontal bar behind, you would reach past the vertical bar just mentioned and move your fingers along the horizontal bar behind from one vertex to the other. I hypothesize that this potential touching informs your visual experience of the bar behind so that your visual experience is that of a ‘bar behind’. The horizontal bar looks ‘behind’ just as a paper shopping bag looks heavy when one knows it contains groceries and looks light when one knows it is empty. This, I take to be one example of Merleau-Ponty’s contention that the different senses fuse together (see his Phenomenology of Perception), a view not totally dissimilar to George Berkeley’s contention that sight and touch are “entangled” (see his A New Theory of Vision). Those willing to sign a waiver releasing the author from any liability for any resulting brain damage might also want to consult a certain Cliff Engle Wirt’s journal article The Concept of the Ecstasis.

But the (more or less) horizontal bar is also experienced as cutting in front of the vertical bar. If the experience ‘behind’ is salient enough, the eye just accepts this, even though there is no visual experience of the horizontal bar coming from behind to wrap itself in front of the vertical bar then back again on its journey to the other vertex. In the physical world, these two states of the horizontal bar exclude one another. The horizontal bar cannot, at the same time, be behind and in front of the vertical bar. The two situations are not compatible.

But the visual experience of ‘horizontal bar in front’ is compatible with the visual experience of ‘horizontal bar behind’. For the situation comprising the one experience can and does hold at the same time as the situation comprising the other experience. That the two situations should be compatible may seem strange at first, but really should not. For just as, as John Searle constantly points out, the visual experience of a blue object need not be itself blue, and the visual experience of a square object need not itself be square, the visual experience of ‘bar simultaneously in front and behind’ need not itself have the (impossible) property ‘simultaneously in front and behind’.

Now visual experiences are of ostensible objects which usually actually exist but sometimes do not. My visual experience of my cat tiger (with a mouse) at my left as I write this has as its ostensible object a cat that actually exist. Tiger, although he is, yes, an ostensible object of my vision, is not merely an ostensible object of my vision.

My visual experience of the periwinkle-pink rhinoceros grazing peacefully at my feet while I write this … er…. I mean, were I to have such a visual experience … is (or rather, would be) of an ostensible object that does not exist. There is in fact no purple rhinoceros grazing, peacefully or otherwise, at my feet. The purple rhinoceros is merely an ostensible object of my vision. Nonetheless, I can still talk about him and even give him a name (say, “Alfred”). I can even get upset if he seems miffed and refuses to show up for a few days.

Likewise, my visual experience of the impossible cube I “see” on my laptop screen is of an ostensible object that in fact does not exist. It is merely an ostensible object. It no more exists in the physical world than does my periwinkle-pink rhinoceros. Even so, it does seem to make sense to talk about impossible cubes. We talk about ‘this impossible cube’ among different, varying impossible cubes (say, some with differently colored bars). An ostensible object is an object, existing or not existing, actual or possible or impossible, that can be talked about

Now I propose that we regard one’s comprehensive actual situation and sub-situations as comprising at least those objects that one is involved with. From this it follows that my comprehensive actual situation and all sub-situations comprise ostensible objects, both merely ostensible objects and more-than-merely-ostensible objects. My involvement with my cat Tiger consists in my bond with him. My involvement with the impossible cube consists in my preoccupation with this object as a possible avenue to show how inconsistent situations can exist.

Now if we allow the situation ‘Cliff in his apartment typing away at the keyboard of his laptop to produce disreputable screeds’ to comprise the superset ‘ostensible objects of perception’, not just the proper subset comprising ‘physical objects existing in time and space’, that situation will contain, as a sub-situation, the impossible cube I visually experience on my screen. The situation comprising this impossible object is not compatible with itself. It is constantly excluding itself. In a way that sounds very Hegelian, it is incoherent, existing in contradiction.

One would expect such an object to be unstable, and this one in fact is. The horizontal bar behind is constantly threatening to become the horizontal bar in front of the vertical bar, with the result that the cube suddenly switches from being vied from above to being viewed from below.

Now let’s take s to be the singleton situation that comprises the impossible cube depicted on my laptop screen. Let A be the proposition expressed by the English sentence “The horizontal bar is behind the vertical bar”. (That this proposition is about the impossible cube is given.) I venture the claim that no situation compatible with s makes A true. For surely the only situation that could possibly (I will leave ‘could possibly’ undefined) make A true is s itself. But as we have just seen, s is not compatible with itself. And surely no situation that is compatible with s will make A true. For example, that Tiger is to my left is compatible with s (this situation holds at the same time as s), but clearly does not make A true. Nor can I think of any other situation apart from s that would make A true.

Therefore, ~A counts as true according to the truth condition for negation stated above. But it is also the case that no situation compatible with s makes ~A true. Only s could make ~A true. For example, that Tiger is lying to the left of me, always about to press his paw onto the keyboard, clearly does not make true ~A, ie., “The horizontal bar is not behind the vertical bar”. But s is not compatible with itself. So ~(~A) is true, which means of course that A is true. So the truth condition for negation gives us the result that a situation exists for which A ^ ~A is true. Inconsistent situations do exist.

This way we can avoid the Classical Logic paradox (A ^ ~A ) –> B. That is to say, from a contradiction every proposition follows — the Principle of Explosion. This principle would, of course, allow for multitudinous irrelevant implications and therefore cannot hold in Relevant Logic. We can avoid the principle of explosion if we maintain that situations comprise ostensible objects, which include not just actual objects, and not just possible objects, but also impossible objects.

Naturally, a possible world cannot contain impossible objects. (Duh.) Unlike situations, possible worlds must be consistent. So, as Mares notes, a possible world must be both complete and consistent:

First, whereas worlds are complete, situations can be incomplete. To use the terminology of Barwise and Perry … worlds decide every issue. That is, they tell us, for any proposition, whether that proposition is true or false. Situations, on the other hand, do not decide every issue. In some situations, the information whether a given proposition [e.g., “Bigfoot roams the forests of western Washington state”] is lacking. This property of situations is sometimes expressed by saying that at some situations ‘the principle of bivalence fails’. Second, situations need not be consistent. That is, there are some situations that make contradictions true. Possible worlds, on the other hand, are completely consistent.

Mares, RL, pl 27

I have tried to use the concept of possible worlds that are epistemically accessible to a knower S as a way of making sense of the concept ‘partial situation’, that is to say ‘non-bivalent situation’. Partial aka non-bivalent situations are ones in which A v ~A and A –> A may not be true. Trimming out all the possible worlds (that is, all the ones not identical with the actual world) that are epistemically accessible to me leaves me with that portion of the actual world about which I have information — Cliff’s comprehensive actual situation. Defining this situation this way already makes it relative to a knower, i.e., a person in a situation. A situation has a center — this person.

Likewise, I have tried to use the concept ‘ostensible object’ to make sense of the concept of an inconsistent situation. As the center of my comprehensive actual situation, my perceptual apparatus gives me the ability to experience ostensible objects that do not exist as well as ostensible objects that do exist. Some of the merely ostensible objects are possible objects (e.g., the purple rhinoceros gazing peacefully at my feet); others are impossible objects (e.g., the impossible cube inspired by Escher). A ^ ~A is true for at least some situations containing impossible objects.

So now Cliff’s comprehensive situation includes more than just the actual world. As a possible world, the actual world cannot contain impossible objects. Containing a surplus, so to speak, over and above the actual world, my comprehensive situation can no longer be described as just a restriction of the actual world. We need now to speak of just ‘Cliff’s comprehensive situation’, leaving out the ‘actual’.

The falsity of A ^ ~A and the truth of A –> A (aka A v ~ A) still hold for possible worlds. So aficionados of the law of the excluded middle and of the principle of non-contradiction need not freak out. These fail to hold only for situations. On the other hand, situations are better suited than possible worlds to account for natural language:

…the ubiquity of expressions that clearly depend on restricted parts of the world gives us reason to believe that natural language is built primarily to talk about restricted parts of the world and not talk about complete possible worlds.

Mares, RL, pl 40

The End: And here I will end this installment of my writing-to-learn project for Mares’ Relevant Logic A Philosophical Interpretation. My tiny fragile bark is already way out as it is in the open sea, trying, far from the safety of any shore, to cope with some huge and frightening waves. I do not need to go any further at the moment. I leave you, gentle reader, with Emil Nolde’s depiction of a person, in their finitude, in the midst of, in the thick of a situation they must grapple with.

Emil Nolde, The Sea I

Lumber Room:

Compatibility/Incompatibility:

What follows is a series of points that I will be trying to shoehorn into this essay as I revise it now that I have hammered it into at least an initial shape.

[[[Let me say that a situation such as the shell #1 situation is epistemically compatible with another situation — say, my comprehensive actual situation — if it is epistemically possible for it and that situation to combine so as to comprise a larger situation. The situation whose defining description forms the key description of the shell #1 possible world is a possible part of my comprehensive actual situation. It is therefore compatible with that situation, and that situation is compatible with it. ]]]

[[[Conversely, every situation that maps to a key description of a spawned-from-the unknown possible world that is not epistemically accessible for me is epistemically incompatible with my comprehensive actual situation. Above, I gave an example of a spawned-from-the unknown possible world in which there is always the possibility of a rogue peanut in one of Elizarraraz’ shell games, taking its cure from the behavior of electrons as described by my undergraduate chemistry TA, ending up on the nose of the Mona Lisa. Given our knowledge that peanuts (nor any other objects on the post-quantum level) do not behave this way in the actual world, we know something that rules out the identity of this possible world with the actual world. The rogue peanut world is not epistemically accessible for me from my location in the actual world, which means that the rogue peanut situation is not compatible with my comprehensive actual situation. To rule out is to exclude; to exclude is to render incompatible. Conversely, to fail to rule out is to fail to exclude; to fail to exclude is to render compatible.]]]

[End with drive towards inconsistent situations?]

. [[[This knowledge may or may not be knowledge that I can access immediately, or even knowledge that I know I have. ]]]

[[[[[[[That the peanut be under shell #1, for example, fits in with, does not conflict with, is not ruled out by the knowledge I have about the actual world. I make this claim rather confidently — in fact, I am willing to bet my paint brushes on its truth. Nonetheless, unless I can be said to both to know and to have at my fingertips everything I know, perhaps I cannot be absolutely certain that in the body of knowledge I possess, there is an item of information that would rule out the the peanut’s being under shell #1 within the currently unknown-to-me part of the actual world. I might, while sleepwalking, for example, have one-twentienth consciously seen Elizarraraz filling shell #1 with cement, rendering the presence of the peanut there physically impossible. (In no possible world nomically accessible from the actual world can a shell filled with cement hide a peanut. I assume.) ]]]]]

[[[[[This visual information might be stored in my brain, ready to pop out at any time, or perhaps accessible only through deep hypnosis, but at any rate information unknowingly possessed by me. In that case, I would possess information that would rule out the situation’s being part of the actual world. This is so even if at the same time I also have the opposite belief. I can be in two cognitive states at the same time whose contents directly contradict one another. This point will become important later when I consider inconsistent situations. ]]]]]]

[[[[[Nonetheless, I rather doubt that anyone would want to gainsay my ‘I know nothing that would ….’ claim should I make it. And certainly there is a fact of the matter regarding whether this claim is true — whether there is nothing in my body of knowledge that would rule out the presence of the peanut under shell #1 in the actual world. ]]]]]]

I[[[The descriptions “the shell is empty” and “the shell hides the peanut” clearly preclude one another; they are metaphysically incompatible. ]]]]] Likewise, I might discover later that what I took to be the hollow of the shell was in fact filled with concrete, rendering its hiding the peanut physically impossible. The descriptions “the shell is filled with concrete” and “the shell hides the peanut” clearly preclude one another; they are physically incompatible.

But until I know things like this, the possible situation in which the peanut lies under shell #1 could be — in some sense of “could be” — a part of the actual world. The ‘could be’ is epistemic, stemming from the epistemic concept of relative ignorance, or lack of knowledge. So far, I do not know anything that would rule out the situation’s being part of the actual world, so this being a part of is still a possibility. Nothing that “automatically precludes from the get-go its being a part of the actual world and therefore something that could eventually be discovered to form part of my comprehensive actual situation.]]]]]

[Logically/metaphysically accessible possible worlds and nomically accessible possible worlds do not need to refer to an agent S. Possible worlds that are epistemically accessible for S do need to refer to an agent S. These are possible worlds that smuggle in the concept of a center. They invite the notion of a situation.]

Two situations are compatible within a possible world at time t if and only if they can (epistemic “can”) hold at the same time within that possible world. Let me produce some examples. [Non-normal situations can be incompatible with themselves. Satisfied descriptions. ]

[[[If my cat Tiger is sitting on a mat (where I have deposited him to keep him off my keyboard) at the same time that the doorbell rings, the situation ‘Tiger is sitting on the mat in my apartment’ is clearly compatible with ‘the doorbell is ringing in my apartment’. That these two situations hold at the same time t in the actual world is proof positive that they are compatible in the actual world at t. Now I know nothing that would rule out the identity with the actual world of the possible world in which this situation in my apartment holds. Which is good, because the actual world is identical with this possible world. The fact that the two situations do hold at the same time in this one possible world, namely, the actual world, shows that they can hold at the same time in this world; and this possibility is (at least) an epistemic possibility. ]]]]

[[[[[[[[[[[[[[[[[[[[[[[[[[Identity a sufficient condition for compatibility for normal situations. Two descriptions — stable. Not flashing this way then the opposite. Not like “This sentence is false”.Bring up the over/under business much much earlier.]]]]]]]]]]]]]]]]]]]]]]]]]]

Now let me circumscribe the rogue peanut world to just one situation s1 within that world, namely, the shell game the Elizarraraz has set up in the Pilsen neighborhood of Chicago, that somber city, within an easy walking distance of Western Avenue.

To rule out is to exclude; to exclude is to render incompatible. submit, then, the following. Our knowledge (at least I hope that is what that is) that rogue peanuts do not exist in the actual world rules out s1‘s being a situation in the actual world. Therefore, s1 excludes my comprehensive actual situation, s0. s1 and s0 are incompatible situations; and s1 is incompatible as well with any situation within s0. To rule out is to exclude; to exclude is to render incompatible. Therefore, no situation drawn from a spawned-from-the-unknown possible world is compatible with my comprehensive actual situation or with any of its sub-situations.

If it were so ruled out. I submit that, conversely, every situation drawn from a possible world that is If it were so ruled out. epistemically accessible for me from my location in the actual world is compatible with my comprehensive actual situation s0 and with every sub-situation of s0. For every such situation is possibly — in the epistemic sense of ‘possible’ noted above (think: ‘the peanut is possibly under shell #1) — a part of the actual world. The description mapping to every such situation fails to get ruled out by my knowledge (if it were so ruled out, it obviously would not be part of a possible world epistemically accessible for me from my location in the actual world). Failing to get ruled out is failing to get excluded is failing to be incompatible. Failing to be incompatible is to be compatible.

[[[[[An example of failing to believe that an item of knowledge is part of my body of knowledge.]]]]]]] Likewise, I may falsely believe that a situation is compatible with my comprehensive actual situation when it fact it is not. Suppose, for example, that I really have taken the eight graduate courses in quantum mechanics (with a grade no lower than a B+ in any of them and I got that B+ in just one of the courses) came in just one course. Suppose, further, that I acquire the knowledge that peanuts cannot, while obeying the laws of nature, behave like electrons in the way described by my undergraduate chemistry TA. But all my friends are still New Age crystal devotees who think that peanuts can behave like electrons and display the same effects as they. In the midst of a party in which I imbibe too much in their company and watch too many You Tube videos with them about quantum physics and stare at too many crystals, the wages of tribal identity set in for a moment and I come to believe during the party that peanuts, which only the moment before had been contently abiding under one of Elizarraraz’ shells, can suddenly find themselves the next moment on the nose of the Mona Lisa. The morning after, I come to my senses, no longer under the intoxicating tribal influence of my peers, and no longer believe this. But during the party I held a belief that conflicted with my knowledge. Beliefs can conflict with other believes and with knowledge.

Even during the party, however, my belief did not determine my comprehensive actual situation. My knowledge, which although not occurrent at the moment, was nonetheless not wiped away by the party, continued to define my comprehensive actual situation. The rogue peanut situation continued to be incompatible with, ruled out by, my comprehensive actual situation.

Satisfaction of a description is important also in analyzing compatibility/incompatibility. The impossible cube is not satisfied by any object in the actual world. Since situations are descriptions (descriptions which are (were/will be) satisfied by the actual world when they are actual situations and not satisfied by the possible world when they are merely possible situations), two situations are compatible | incompatible in a possible world if their defining descriptions can be | cannot be satisfied in that world.

[Why use epistemic could and not, say nomic could? Because we are talking in finite situations. So at least theoretically two situations could be epistemically compatible but nomically incompatible. I submit, however, that we should stick to the epistemic notion of compatibility in analyzing human language and human coping with the world. That my neighbors’ walls could be cornflower blue is quite live and real for me. And, as I will show in a moment, one can use that ‘could’ to provide the truth conditions for “not” in the sentence “The walls of my apartment are not fuchsia” that can be comprehended by a finite human being. The corresponding nomic ‘could’ cannot be used that way. ]

[Finite situations appropriate for human language. This is a concept of compatibility that is in harmony with the notion of situations, which emphasizes their local and fragmentary character. My situation is a bunch of so far as I knows. My situation does not comprise the entire actual world because I am not omniscient. ]

[Henceforth, unless otherwise noted, I will be using “compatible” to mean “epistemically compatible”.]

Cannot be satisfied at the same time. My apartment walls cannot be portobello mushroom and fuchsia at the same time. The two descriptions are not compatible. They cannot be fulfilled by any situation in the actual world at the same time. The portobello mushroom situation and the fuchsia situation cannot obtain in the same possible world.

Identity in satisfied situations and simultaneity, then, are two sufficient conditions for compatibility. But there is a third sufficient condition that I want to consider, namely ignorance, my not knowing everything. Nomic and initial conditions example.

There is nothing so far in what I know that would render the description ruled out by what I know.

Truth:

[[[Situations whose boundaries are determined by the limits of one’s knowledge would divide the actual world into what is exposed to one — the finite situation itself — the dense part of the lump of cheese, the mesa surrounded by the fog — and everything that is hidden from one — the holes in the lump of swiss cheese; the fog surrounding the mesa.]]]

[[[Is the truth of the sentence a matter of change from the perspective of one’s own situation? If yes, then one’s own situation is not making the sentence true. Truth is never a gamble]]]

[[[There is no doubt that there are three shells before my eyes. This is so even if ‘there are three shells before my eyes’ is defeasible. If 1 through 4 have credences of less than 1, every exposed state of affairs within my comprehensive actual situation has a credence of 1. There is no doubt that there are three shells before my eyes. This is so even if defeasible. A credence is a number that is assigned; and I shall assign a credence of 1 to all those states of affairs in my comprehensive actual situation for which any doubt seems merely theoretical, not to be taken seriously in the course of one’s affairs. David Hume, for example would or at least should, assign a credence of 1 to the billiard table and the balls when he gets up from his skeptical studies to play a game of billiards. Certainly he would know nothing that would rule out the identity with the actual world the possible world in which the pool table actually does exist in space/time. But to discuss this further would take me too far afield.]]]

[[[Now if there is anything that could serve as a conduit of information between the hidden situation and my comprehensive actual situation such that states of affairs in the former could become exposed to me in my position in the latter, the probability-as-credence of this state affairs would increase to 1. If my neighbor is completely reliable, for example, the color of his walls would become exposed to me were he to tell me they are wine red. The probability/credence that they are wine red would increase from 1 divided by the number of paint colors to 1. That the walls are this color then becomes part of my comprehensive actual situation.]]]

[[[For a sentence to “reach out” so to speak to a hidden situation and to be ‘made true’ is for the probability/credence to increase to 1 from a lesser number. For a sentence that is about a state of affairs within a finite situation to be made true, it needs to have already been exposed and the garden-variety credence given to it to be 1 already. For a situation to make a sentence true is for the sentence to correspond to an exposed state of affairs.]]]

Within my comprehensive actual situation, the resources are lacking to make 1 through 4 true. As I will show when I get to the truth condition for negation, the resources are also lacking within that situation to make the negations of 1 through 4 true. Let A be any of the sentences 1 through 4. A is not true. If we adhere to a 2-valued logic, this means that A is false within the situation. But, as I will show, the situation also fails to make ~A true. So ~A is also false within the situation. A v ~A would be false because both A and ~A would be false. Bivalence would fail for my comprehensive actual situation.

And once it is turned over, it will be the case, I am rather inclined to think, that nothing in my body of knowledge rules out the identity with the actual world of the possible world in which the peanut always was (from the time Elizarraraz placed it under one of the three shells) present | not present under shell #1 the whole time. But there is something in my body of knowledge that rules out the identity with the actual world of the possible world in which the peanut was present | not present under the shell the entire time — namely, that peanuts do not behave like electrons. Or at least I hope that I know this. I might add parenthetically, by the way, that whether this really is an item in my body of knowledge is independent of whether I believe it to be.

[[[Need to discussion situation types vs. individual situations]]]

So while nothing in my comprehensive actual situation makes it true that either A (“the peanut is under shell #1”) or makes it true that ~A (“it is not the case that the peanut is under shell #1”), one is likely to be proceeding on the strong assumption that this is so. But if we confine ourselves to just the situation, the situation does not have the resources to make either A or ~A true.

[[[Within the worldly situation of such a being, every sentence would either be made true within the situation or fail to be made true. The probability of 1 through 4 each would be 1.]]]

[[[The epistemic version of truth, i.e., the correspondence to something actual, would then be the correspondence to something known to be actual.]]]

[[[So we have local truth on the one hand and global truth on the other. Local truth is not relative truth.]]]

Bivalence

[[Exposure makes the epistemically accessible situation a part of s0. I asserted above that a situation such as the shell #1 situation is epistemically compatible with another situation — say, my comprehensive actual situation — if it is epistemically possible for it and that situation to combine so as to comprise a larger situation. It could be (epistemic could) the case that the peanut is under shell #1, in which case the presence of the peanut there would become, upon exposure (say by turning over the shell or through a sonar device that is designed to detect the presence of peanuts under shells) a part of s0. Or it could be (again, epistemic could) the case that the peanut is not under shell #1, in which base the absence of the peanut there would be what becomes part of my comprehensive actual situation. ]]

[[That the walls of my apartment are portobello mushroom has already gotten exposed in the situation comprising my apartment in particular and in my comprehensive actual situation in general. Even if somehow I haven’t really noticed the color of my apartment walls (say, when I entered the apartment for the very first time), nothing blocks me from focusing my attention on it for a moment and saying “Aha, portobello mushroom”. The color of my apartment walls lies exposed in my situation. ]]

[[[Situations drawn from possible worlds epistemically accessible to S from their position in the actual world are the graveyard for the truth of A v ~A.]]] [[[Important that on my account the compatibility relation could hold between situations in different possible worlds, as long as the situations could be part of the actual world. I don’t know what trouble this will pose for me. Important to discuss the Tiger from a different planet possible world.]]]

[[[But every other sentient being is situated, that is to say, is plunged into a concrete situation that has them as its center and from whom much is hidden, and to whom some is exposed.]]]


Dissolving The Monty Hall Paradox

My intent in the following is to dissolve the paradoxical character of the Monty Hall game and to explain WHY it may seem so paradoxical at first.

I turn the Monty Hall paradox into a shell game. I do this partly because I loathe cars (the original game was a TV show in which the guest had to choose one of three doors. A car was behind one door; a goat was behind each of the remaining two doors). And partly because the traditional slipperiness of shell games fits my “insight” (or maybe it is a delusion).

Three shells are in front of me, one of which hides a peanut. My task is to select a shell in the hopes of uncovering the peanut. In the normal shell game, that is where the game ends — the selected shell is either hiding the peanut or it is empty. In a shell game of the Monty Hall persuasion, however, the person setting up the game (call him Elizarraraz), instead of turning over the selected shell to reveal what it is hiding | alternatively not hiding, turns over instead a shell which he knows to be empty. I am to choose one of the remaining shells.

None of the three shells is perceptually distinguishable for me from the others, except when Elizarraraz labels them with different sets of tags, a task which Elizarraraz performs honestly and reliably. There will be three sets of tags. Each of these sets defines a different shell game of the Monty Hall persuasion.

Each of the three games is to be repeated in ten million times. (A bit exhausting, perhaps, but this is a thought experiment after all.) In each of these ten million iterations of each game, Elizarraraz uses some randomizing device to choose under which shell to place the peanut.

In the first game, Elizarraraz labels the shells #1, #2, and #3. Each of these shells has an identity based on its trajectory through four-dimensional space/time. As anyone who has read the popular literature on Einstein’s Relativity Theory (by the way, my knowledge of the theory goes no deeper than this) knows, objects with mass are continually moving through at least one dimension, and possibly through all four (the dimensions typically plotted on the graph with x, y, and z axes, plus the temporal dimension) at once. When it is in everyday thought and speech regarded as at rest, it is in fact still moving through time. Each of the three shells has its own trajectory through the four dimensions of space-time which individuates it. I will call this identity of the shells their “natural identity”.

I select a shell. Elizarraraz now turns over a shell he knows to be empty, and tells me to select again. I choose by employing a randomizer through each of the ten million iterations of the game. My strong intuition, which I have yet to prove in at least a quasi-mathematical way, is that out of the ten million iterations, 1/3 of the time, shell #1 is hiding the peanut, and 1/3 of the time shell #2 is hiding the peanut, and 1/3 of the time shell #3 is hiding the peanut. The possibility space (aka sample space) is {shell#1p shell#2p, shell#3p}. This set has a cardinality of 3, and the probability functions assigns a value of 1/3 to each member of this set. (Or so I am confident I will eventually prove.)

In the second game, Elizarraraz labels the remaining shells ‘shell A’ and shell B’. He employs a randomizing device to choose which of the remaining shells to attach which label to. In doing so, he creates two “artificial” objects, shell A and shell B. Each of these shells has during any given iteration of the game a part, which can be either shell #1, shell #2, or shell #3. I will call these parts temporal parts. As befits the slippery character of the classical shell game as one may once have encountered it on the EL in Chicago, in which the maybe-not-totally trustworthy person who sets the game in motion through their sleight of hand relies on the difficulty in perceiving any differences among the shells, the individuating trajectory through space-time described in the first game above is not important here. The temporal parts of shell A | alternatively shell B fuse together, so to speak, to form for shell A | B a single object. This is not a “natural” object, a “natural” identity, but an “artificial” one.

Let me provide another example of an artificial identity. In a certain Pho restaurant in Houston I used to frequent before the pandemic, the employee behind the cash register would take my order, then hand me a sign on which was printed, say; “table #6”. I could place that sign on any non-occupied table I wanted. Those tables are individuated by their trajectory through space-time as various customers place it on various tables, but they also serve as temporal parts for an artificial object, an artificial identity named “Table #6”. Shells A and B are like Table #6.

Or again, suppose that a a population chose each year a different individual to be its king — but for whatever reasons rooted in their mythology thought of the king as ‘the same king’ throughout the years. Or again — one more time — a novelist might emphasize the humdrum uneventfulness of the passage of time for a character by making the character not think of the proprietor of the dry-cleaning shop they frequent as different people even when in fact they are different people. The difference is not salient for the character. Shell A | shell B is an artificial object like the king or the fictional proprietor of the dry-cleaning establishment.

My strong intuition, which I have yet to prove in at least a quasi-mathematical way, is that out of the ten million iterations, 1/2 of the time, remaining shell A will turn out to be hiding the peanut, and 1/2 of the time remaining shell #2 will turn out to be hiding the peanut. Here the possibility space for the game is the set {shellAp, shellBp}. The possibility space has a cardinality of 2, and the probability function assigns to each member of this set a value of 1/2. (Or so I am confident I will eventually prove.)

In the third game, Elizarraraz labels the remaining shells as ‘initial choice’ and ‘switched choice’. This time the choice of label is made on the basis of the shell’s actual history, not on the basis of a randomizing device. Again, each shell so labelled could be shell #1, shell #2, or shell #3 — I am not able to tell because I cannot distinguish the shells without the labels. This is a shell game, remember, the whole point of which is to be slippery.

Out of the ten million iterations, 1/3 of the time the peanut will be under the shell labeled ‘Cliff’s initial choice’, and 2/3 of the time the peanut will be under the shell labelled ‘Not Cliff’s initial choice.’ This has been proven time and time again. The mathematician Paul Erdos (the guy who is a machine for turning coffee into theorems) was at first skeptical, but became convinced once he saw that computer simulations of the game, repeated ten million times, result in the peanut being under the initial-choice shell 1/3 of the time and under the switched-to shell 2/3 of the time. The computer simulations are completely dispositive for this result.

Ten million repetitions of the game in a computer simulation will confront you with the brute fact that the ratios are 1/3 and 2/3. But you can also “see” the with the mind’s eye the necessity of this result using tree diagrams like the one shown here, a method that reminds me a bit of Jorge Luis Borges’ THE GARDEN OF FORKING PATHS.

To get the proof down to a more concrete level, appealing, not just to the mind’s eye of the intellect, but also to the senses of sight, touch, and hearing, picture, then draw a system of branching metal pipes (which one can feel as well as see) oriented downward. A drop of water enters the system at the top. As the drop rolls down, it encounters various junctions, which are either “tridents” or forks. The forks arise when one pipe is closed off, mirroring Elizarraraz’ turning over a shell that he knows to be empty. Which pipe the drop flows down is a matter of chance (either 1 in 3 or 1 in 2). One set of pipes mirrors my sticking to my initial choice of shells. Another set mirrors my switching to the other shell. The first set of pipes leads to a coffee can labelled ‘initial choice’. The second set of pipes leads to a coffee can labelled ‘switched choice’. Were a drop of water to be introduced ten million times (okay, ten million and three times) into the system of pipes that the drawing schematizes, one would hear the drop plop into the ‘initial choice’ can 1/3 of the time, and into the ‘switched choice’ can 2/3 of the time.

These two cans have natural identities. That is to say, their identity is determined by their trajectory through the four dimensions of space/time. That their identities are natural, not artificial, may make the 1/3 | 2/3 result more intuitive.

The possibility space for the cans with their natural identifies is {initial_choice_can, switched_to can} In that set, the probability function assigns the value 1/3 to the initial_choice can, and value of 2/3 to the switched_to can. Likewise, the possibility space for the shells, with their artificial identities, is {initially_chosen_shell, switch_to_shell}. In that set, the probability function assigns the value 1/3 to the initially_chosen_shell, and a value of 2/3 to the switched_to_shell.

The complex character of the artificial identities of the “shells” in the second and third games means that those “shells” are constantly switching out and exchanging, so to speak, their temporal parts. For any given repetition of the second game, the current temporal part of shell A might be shell #1 and that of shell B might be shell #3 [In creating the artificial identities, we are “assembling” them from parts]

With any luck, I have dispelled the drastically counter-intuitive nature of the Monty Hall shell game. By now, it should also be plain why this game seems at first to be so frigging paradoxical. It will only seem paradoxical if one confuses the third game with the second game.

These are two different games, but it is easy to confuse them. Here are the two shells facing me in the moment after all — OF COURSE if I ignore their history I will thinking of them (whether the corresponding labels have been applied to them or not) as ‘remaining shell A’ and ‘remaining shell B’. Under THAT description, the probability really is 1/2. The only way I could decide between the two would be to flip a coin, since the information expressed by the descriptions ‘initially chosen’ and ‘switched to’ is not available to me. So, as the two shells face me in the moment, sneering at me, making me forget the entire tree of tridenting and forking possible paths the shells could be taking during the ten million iterations, OF COURSE I will be thinking (wrongly) that my chances will be 50/50 regardless. But as Judea Perl notes, much as the statisticians (he claims) loathe the idea, the history of an entity counts in determining probabilities. It does so by determining both what is contained in the set comprising the possibility space, and the values assigned to those artificial identities by the probability function. Once the history-determined artificial identities of these two entities ‘shell initially chosen by Cliff’ and ‘shell not initially chosen by Cliff’ becomes available to me, the probabilities are no longer 50/50, but 1/3 or 2/3 respectively.

The three different games are indeed three different games, each with different entities in their sample space and different probability functions assigning different values to those entities. The confusion of the three games with their corresponding possibility spaces is what creates the sense of paradox.

Links

Ternary relation and conditionality