Category Archives: Formal Semantics

Selectors And Semantic vs. Syntactic Arguments

In case anyone wonders (“feel free to come to the point when you finally decide what it is”), the point of the following ramblings is to arrive at a place where I can make a distinction between semantic arguments and syntactic arguments.  The point of making this distinction will become clear (or not) in a later post.  Making the distinction is part of my attempting to put in my own words the argument that Tagalog lacks a subject.

In the previous post, I argued (or claimed, or made the completely unsupported, nay, spurious assertion, as the case may be) that the semantics of Maganda si Robert Pattinson can also be given by the following statement in the database language Tutorial D:

GORGEOUS_EQUALS_GORGEOUS{THIS_ONE, THAT_ONE} where THIS_ONE = PERSON(NAME(‘Robert Pattinson’))

This statement includes the Selector PERSON(NAME(‘Robert Pattinson’)).  Let me unpack a bit what this is. Before I start, I’d like to point out that I THINK that it is  legal in Tutorial D to nest one selector inside another…

NAME(‘Robert Pattinson’) is a operator or function that takes the string ‘Robert Pattinson’ and selects one and only one name.  I will take the concept ‘selects’ as primitive here.  Any implementation of this selector in a physical computer would involve shuffling around ones and zeros until the computer spits out, i.e., returns, one member of the set NAME.  NAME would include strings, but subject to certain limitations.  For example, I assume a  name would have to be, at least, less than 1 billion characters long.  NAME would also include more than strings (that is, representations of text):  a name can be selected by a sound.  So NAME(<<some representation of a sound>>) could also select the name Robert Pattinson. (The reader will notice that I have not yet decided on how to represent, in the absence of a formal selector, a name as opposed to a string as opposed to the person himself…)

PERSON(NAME(Robert Pattinson)) would take the name selected by NAME(‘Robert Pattinson’) and return a member of the set PERSONS, i.e., Robert Pattinson himself.  I don’t know how a computer would implement this operator, but a human being would be implementing that operator in the following type of circumstance:  say, I am sitting in a restaurant.  Someone in the table next to me says:

 I hereby officially declare myself to belong to Team Edward because Robert Pattinson is just too gorgeous.

One part of that utterance, the part that I hear as the word ‘Robert Pattinson’, is the end point of a long causal chain that begins, say, when the parents of Robert Pattinson, after endless wrangling and indecision, finally agree to call their baby ‘Robert’; the doctor in the Maternity Ward crosses out the ‘baby boy’ in ‘baby boy Pattinson’ and writes in  ‘Robert’ on the birth certificate (call this the ‘baptismal event’) … endless events … a director or producer chooses the person named by ‘Robert Pattinson’ to play Edward Cullen in TWILIGHT … endless events…the person sitting at the table next to me sees TWILIGHT…he reads in a magazine he buys at the supermarket that Robert Pattinson played the part of Edward Cullen…he emits a set of soundwaves at the table next to me, which in turn trigger God-only-knows what processes in my brain, until I hear ‘…Robert Pattinson….’  That entire causal chain, ending up in the wetware of my brain, selects the person Robert Pattinson.  THAT’s the implementation of the selector PERSON(NAME(<<some representation of certain sound waves>>)).  Speaking metaphorically and a bit picturesquely, the selector spits out, or returns, Robert Pattinson himself, the flesh-and-blood Robert Pattinson who lives in (I would say ‘Valencia, California’, but that is where Taylor Lautner lives)…. Speaking literally, the selector selects Robert Pattinson himself.

(See Saul Kripke, who apparently never explicitly endorsed this causal theory of reference aka selection.  Gareth Evans would apparently deem this theory, as stated by me, to be naive, but it seems perfectly intuitive to me.)

Invocations of selectors produce literals (more accurately, I guess, are literals).  So whatever else Robert Pattinson himself may be, he is a literal value.

Let me take the liberty of allowing selector invocations as arguments supplied to the parameters of functions, so that we can replace x with the argument PERSON(NAME(‘Robert Pattinson’)) in the function x EQUALS x to produce a true proposition.  Below, I have identified, ala Chisholm, propositions with states of affairs in the world:  here, with Robert Pattinson being identical with Robert Pattinson.  This proposition gives us the semantics of the utterance “Robert Pattinson equals Robert Pattinson.”

I will therefore call the invocation of PERSON(NAME(‘Robert Pattinson’)) a semantic argument.  By contrast, the invocation of NAME(‘Robert Pattinson’), occuring inside an utterance, spoken or written, is a syntactic argument.  In this way, I make sense of the semantic arguments vs. syntactic arguments distinction I puzzled over in a previous post.

I do not know, of course, whether this is the distinction that Beatrice Santorini wanted to make.

I will end by making another homage to Plato’s SYMPOSIUM, according to which interest in Robert Pattinson, Taylor Lautner, Kellan Lutz et al ultimately leads to interest in the Relational Algebra, and from there, to the Form of Beauty itself:

Robert_Pattinson_2

Wow, I love that slightly-unshaven look…(the reader may  hear a rapturous sigh…)

Now, having briefly lapsed into a lower form of eros, I will go back to eros for the Relational Algebra in connection with Semantics….

Update:  After hitting the publish button, I saw this quote from the first Jewish Prime Minister of Great Britain:

The best way to become acquainted with a subject is to write a book about it.

Benjamin Disraeli

Or blog about it at length.

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The Mystery Of The Missing IS: Or, Had John Duns Scotus Been An Ordinary-Language Philosopher Working In Tagalog


Below, I have tried to start incubating the suspicion that there is something fishy about treating ‘is’ as a predicate with two parameters accepting one argument each, i.e., a two-place relation.


Tagalog doesn’t have a verb ‘is’, no verb ‘to be’.  Given that more literal translations of Tagalog sentences often display the phrase ang noun phrase structure as:

 

phrase [is] ang noun phrase


For example:

Titser ang babae.

Maganda ang lalaki.

Umalis ang babae.

gets rendered as:

Teacher [is] the woman.

Beautiful [is] the man.

Having left [is] the woman.

or as I prefer (see my attempt below at eliciting the ‘aha erlebniss’):

Some teacher one  [is] the woman.

Some beautiful one [is] the man.

Some having left one [is] the woman.

…given that, one might think that, always, the suspect verb aka predicate aka relation is implicitly in effect in sentences with that structure.  The lack of a verb ‘to be’, of an ‘is’ in Tagalog that so perplexed the first Spanish grammarians of the language (so that, in their total confusion and lack of understanding, they tried to interpret the Tagalog inversion marker ‘ay‘ as the verb ‘is’, a confusion and misinterpretation that has had hilarious consequences lasting to this day), is always there, just unpronounced (or unwritten).  The space between ‘maganda‘ and ‘ang lalaki‘ in the written sentence, or the lack of interruption in the string of sounds (if that is how maganda ang lalaki gets pronounced — I am not strong enough presently in Tagalog to know) or the glottal interruption (if one exists between the ‘maganda‘ and ‘ang lalaki‘)  … the space, or lack of interruption in the continuous stream of sound, or the glottal, these are, as the case may be, an implicit sign of the two-place relation ‘is’.

Following Naylor, Schachter, and my own intuition, I have been treating the space, the lack of interruption in the continuous stream of sound, the glottal as an implicit equals.  For example, I prefer to translate the above three Tagalog sentences as:

Some teacher one  = the woman.

Some beautiful one = the man.

Some having left one = the woman.

Unlike ‘is’, however, which is (if there is such a critter) a two-place relation, ‘equals’ (alternatively, ‘=’ ) is, as I am about to show, a one place relation.  It is not just that the sign corresponding to ‘is’ is lacking in Tagalog:  the (real or putative) semantics of ‘is’ is lacking in Tagalog as well.  Tagalog is working with something completely different.

Clearly the ‘equals’ that is in play here is not given by the ‘equals’ in the following two-place relation:

 

THISTHAT

EQUALS (0)
Morning Star Evening Star
3 3
Rose With Barcode 3185321 Rose With Barcode 3185321
Clifford Wirt Clifford Wirt
The murderer of Jones The butler

…because in sentences such as Maganda si Taylor Lautner, the word ‘Maganda’  does not, at the moment of its utterance, specify, identify, locate, expose, or pick out any one particular thing.   ‘Maganda’ is equivalent to ‘Some beautiful one’, or the part of the formal sentence below that occurs before the ‘=’:

∃x ∈ MAGANDA: x = si Taylor Lautner.

The x that belongs to the set MAGANDA is left unspecified, unidentified, unlocated, unexposed, un-picked-out at the start:  Maganda … though it does get specified at the end:  …si Taylor Lautner.  But a two-place relation requires two identified, specified arguments for its two attributes.

Let me try to capture in D the sentence ‘∃x ∈ MAGANDA: x = si Taylor Lautner’.  Let me posit the following 1-place relation:


MAGANDA (0)
MAGANDANG_BAGAY
Taylor Lautner
Sunset at time t and place p
Rose With Barcode 3185321
Wine Red
The Taj Mahal
Haendel’s Umbra Mai Fu

Taking this relation as my springboard, I capture ∃x ∈ MAGANDA as MAGANDA{} (which gives us TABLE_DEE, or TRUE, or YES), then do a CARTESIAN PRODUCT of that with a restriction of MAGANDA:

with
MAGANDA{} as t_sub_0,
MAGANDA{MAGANDANG_BAGAY} where   MAGANDANG_BAGAY= ‘Taylor    Lautner’ as t_sub_1:
t_sub_0 X t_sub_1

CARTESIAN PRODUCT is a special case of JOIN.  TABLE_DEE JOIN r, where r is any relation, yields r.  So the D statement above yields:

MAGANDA (1)
MAGANDANG_BAGAY
Taylor Lautner

which expresses the semantics of the sentence ‘Maganda si Taylor Lautner’.  In this way, we get rid of the doubtful (I think) verb aka two-place relation ‘is’.

To sum up, a bit impishly:  the semantics of ‘is’ is different in Tagalog than in English because Tagalog really doesn’t have an ‘is’.  Later, I will try to develop this into part of an argument that Tagalog lacks a subject.  Tagalog’s lacking a verb ‘to be’ is related to its lacking a subject.

To stray back for a moment to philosophy:  were Duns Scotus an ordinary-language philosopher working in Tagalog, it may never have occurred to him to try to find a single relation (e.g. ‘contracts’ ) between the entity Beauty, as the argument on one side of the predicate ‘is’, and Taylor Lautner as the argument on the other side of the predicate, and so on for every other proposition formed by supplying arguments to the parameters x and y in the predicate x is y.

11/10/2012:  Updated to make a point a bit more clearly.

11/10/2012:  Updated to parenthetically add some snark about the first Spanish grammarians of the Tagalog language in the 1600’s.

 

Update:  11/25/2012:  Post grayed-out because I am dissatisfied with it.


The Relational Algebra Gives Us Something (Or Somebody, Or At Least Someone)

Now onto trying to show how the Relational Algebra gives us ‘something’, ‘somebody’, ‘someone’, and so on.

When I talk about database relations in the following, I am, unless I state otherwise, talking about the abstract object, not those relations concretely realized in an RDBMS.

A brief explanation of the Relational Algebra:  Posit a world all of whose people are members of the set {John, Cliff, Charles, Genghis Khan, Leon Trotsky}.  Moreover, suppose that currently, the predicate:

 x is standing to the left of y

generates the Database Relation pictured below when all the members of this set are substituted for the parameters x and y:

TO_THE_LEFT_OF (0)
PERSON_ON_THE_LEFT PERSON_ON_THE_RIGHT
Charles Genghis Khan
Dan Leon Trotsky
Cliff Genghis Khan

(The above picture, by the way, is just that — a picture of the Relation.  It is not the Relation itself.)  As indicated by the number 0 in the name, this Relation is a base Relation, i.e., what we have before any operations are applied to it.

The Relational Algebraic operation RESTRICT is a function that takes the Relation pictured above as input and produces another Relation as output.  For example, the following RESTRICTion, expressed in Tutorial D:

TO_THE_LEFT_OF where PERSON_ON_THE_LEFT = ‘Charles’;  (Yes, I’ve suddenly gone from the flesh and blood Charles as member of a set to the name ‘Charles’; God only knows what confusions this sudden shift will introduce.)

generates the Relation pictured below:

TO_THE_LEFT_OF (1)
PERSON_ON_THE_LEFT PERSON_ON_THE_RIGHT
Charles Genghis Khan
Dan Leon Trotsky
Cliff Genghis Khan

The operation RESTRICT has given us a Relation comprising a single proposition expressed by the sentence ‘Charles is standing to the left of Genghis Khan.’  As indicated by the number 1, this is a Derived Relation, produced as output from a function that took as input the Base Relation.  The charcoal-grayed out portions of the picture are meant to convey that the derived relation is tied to the base relation in a way in which I will discuss later.

As with RESTRICT, the Relational Algebraic operation PROJECT takes the Base Relation as input and generates a Derived Relation as output.  The following RESTRICT and PROJECT operations, expressed in Tutorial D:

(TO_THE_LEFT_OF where PERSON_ON_THE_LEFT = ‘Charles’ ){PERSON_ON_THE_LEFT}

generates the Relation pictured below:

TO_THE_LEFT_OF (2)
PERSON_ON_THE_LEFT PERSON_ON_THE_RIGHT
Charles Genghis Khan
Dan Leon Trotsky
Cliff Genghis Khan

whose body is the set containing the tuple or proposition expressed by the sentence “Charles is to the left of somebody.”

But wait — all we see in this picture is the value Charles.  (Or, more precisely, the name ‘Charles’ appearing as a set of black pixels on a screen.)  Isn’t this a tuple in a one-place relation?  And if it is, wouldn’t it be a proposition belonging to one-place relation, a proposition such as “Charles laughs”, or “Charles runs”, or “Charles eats”?

Well, if it were such, it could be any proposition belonging to a one-place relation.  The only way to constrain which proposition this tuple is to just one proposition is to place it in its context, the source from which it is derived, i.e., the base relation TO_THE_LEFT_OF.  By performing the Projection, we are for the moment blacking-out the identity of Genghis Khan, the person to whom Charles is to the left, so that we can focus on the identity of Charles.  But we haven’t forgotten that we are working with the relation TO_THE_LEFT_OF, so we know that Charles is to the left of somebody.  We haven’t suddenly switched to the relations LAUGHS, or RUNS, or EATS.

To turn for the moment for relations concretely implemented in an RDBMS running in some stuff made out of the same substance as the red paint on the Golden Gate Bridge, complete chaos would ensue, the world would become a topsy-turvey place, objects would start falling up, if, say, a Projection on EMPLOYEE_NAME in the EMPLOYEE (select EMPLOYEE_NAME from EMPLOYEE) would result, not in the set of people employed by the company (more precisely, the set of propositions ‘John, employee of Widgets_R_US’, ‘Jesse, employee of Widgets_R_US’, and so on), but the set of people designated to live on Mars one moment, the set of ambassadors to Vietnam the next moment, and the set of of Pulitzer Prize winners the third moment.

So the meaning of a Projection on an attribute (“column”) of a relation is constrained by the relation from which it is standing out (“projecting”), so to speak.  The derived relation never ceases to, well, derive its meaning from the base relation.  It never ceases to be a derived relation.  Charles never ceases to be one member of a pair whose member on his right is being ignored or blacked-out for the moment.

(Compare this argument with C.J. Date’s argument in LOGIC AND DATABASES, pp. 387-391.)

Let’s trace then what happens, in this relational model, when we plug in Charles to replace x in the predicate:

Person x, to the left of somebody

The ‘somebody’ is not a parameter — no argument gets plugged into it — but it along with the x indicate that the base relation we are dealing with is TO_THE_LEFT_OF.  It tells us that one of the ‘central participants in the situation’ is some person to the right.  The relevant Relational Algebra Operations — the relevant RESTRICT and the relevant PROJECT — are then performed to generate the proposition:

Charles, to the left of somebody.

According to the Closed World Assumption, a Relation contains all and only those tuples — those propositions — those states of affairs — that obtain, and for which plugging in arguments to the parameters of the predicate defining the Relation results in a true sentence.  Therefore, each tuple in the Relation is paired with the truth value TRUE, and of course, within the Range comprising the two truth values, only the truth value TRUE.

So the set of tuples in a Relation and the set of Truth Values is a function.  So, finally — if I may end this string of ‘therefores’ and ‘so’s’ (“Feel free to come to the point when you finally decide what it is, I hear someone say”), when a single tuple is selected, as was done when the RESTRICT and PROJECT were performed on the Relation TO_THE_LEFT_OF, we can see this as the application of the function on that tuple, an application which returns TRUE.  So (this really is the final ‘so’ — I promise) plugging in the argument ‘Charles’ into the parameter x in the predicate:

x is to the left of somebody

triggers a RESTRICT and PROJECT on the Relation TO_THE_LEFT_OF, which in turn constitutes a selection of a single tuple in that relation, which in turn returns TRUE, which lets us regard the predicate as a function returning TRUE when ‘Charles’ is plugged into the parameter marked by x.

Just so, when the RESTRICT and PROJECT fail to select a tuple, as it does when we substitute ‘John’ for x (John is standing to the right of everyone else, including Genghis Khan), FALSE is returned.

Voila!  We now we have somebody (or, as the case may be, nobody).

It is clear that the predicate:

x is to the left of y

can be treated the same way.

Treating verbs aka predicates relationally this way — that is, as functions implemented by Relations and operations on Relations — has two advantages over simply seeing them as functions in the way described by Kroch and Santorini.  First, we get a semantics for ‘somebody’, ‘something’, etc.  Second, we have a way of conceptualizing in terms of operations of the Relational Algebra the select that occurs when, to use the verb laughs as our example, Luke is selected and the truth value TRUE is returned.  The notion of select is no longer a primitive.

 

Updated on 05/10/2012 to correct an obvious oversight.


And One More Thing Before I Move On

It seems to me Kroch’s and Santorini’s rendition of this function:

(1)     [[ invite ]] = { Chris Andrew T ) ,
  David Andrew T ) ,
  Eddie Andrew F ) ,
  Chris Brian F ) ,
  David Brian F ) ,
  Eddie Brian T ) }

is off, since in a function the first entity in a given ordered pair can be mapped to one and only one entity.

Shouldn’t the function be represented this way:

(2)     [[ invite ]] = { Chris { ( Andrew T ) , ( Brian F ) , . . . }
  David Andrew T ) , ( Brian F ) , . . . }
  Eddie Andrew F ) , ( Brian T ) , . . . }
}                  

?

Or am I missing something obvious?


Trying To Make The Problem A Bit Clearer

In the hopes of making it a bit clearer why it is a problem, let me restate the question that I think the Relational Algebra will resolve.

So far we have been modeling sentences in which nothing is left unspecified.  Chris invites AndrewLukas laughs.  How could we model, however, sentences such as Chris invited someone, Someone invited Andrew, Someone invited someone, Joe ate something, Someone laughed … sentences in which at least one of the “central participants in a situation” is left unspecified?

‘Somebody’, ‘someone’, ‘something’ and so on pose a problem for the model presented in the post The Verb Considered As A Function.  Sets always comprise definite, clear-cut individuals.  Since functions are sets of ordered pairs, the primary and recursive functions discussed so far are pairings of definite entities.  What would it mean anyway to have a function that included an indefinite or unknown, entity, as if some function could be pictured this way:
 
brackets instead.

(1)     [[ laugh ]] = {   T,
    F,
  Eva F,
    T,
  Lukas T,
  Tina T }

?

How would we model a sentence “Somebody laughed” that is true, and a corresponding sentence “Somebody laughed” that is false?

 


The Predicate As A Truth Valued Function

So far we have been modeling sentences in which nothing is left unspecified.  Chris invites AndrewLukas laughs.  How could we model, however, sentences such as Chris invited someone, Someone invited Andrew, Someone invited someone, Joe ate something, Someone laughed … sentences in which at least one of the “central participants in a situation” is left unspecified?  We can model these sentences, I think, by applying the Relational Algebra to them — or, more precisely, to the propositions that underlie them.  In this post, I start laying the groundwork for showing how we can use the Relational Algebra to model sentences containing ‘someone’, ‘anyone’, and the like.

Let me begin by outlining the key premise behind Relational Database Theory: 

Predicates generate propositions which are either true or false.  A given Database Relation comprises all and only the true propositions generated by a given predicate.  (This is the Closed World Assumption.)  We can apply various operations of the Relational Algebra to the propositions contained in a Database Relation.

The key premise in Relational Database Theory talks about predicates.  What, then, is a predicate?

What the database theorist C.J. Date calls a predicate is what Kroch and Santorini call, in the primer on Chomskyan linguistics quoted from in the post below (The Verb Considered As A Function) a verb.  Date explains what a predicate is better than I can, so let him speak (LOGIC AND DATABASES THE ROOTS OF RELATIONAL THEORY, Trafford Publishing, Canada, 2007, p. 11):
 

A predicate in logic is a truth valued function.

In other words, a predicate is a function that, when invoked, returns a truth value.  Like all functions, it has a set of parameters; when it’s invoked, arguments are substituted for the parameters; substituting arguments for the parameters effectively converts the predicate into a proposition; and we say the arguments satisfy the predicate if and only if that proposition is true.  For example, the argument the sun satisfies the predicate “x is a star,” while the argument the moon does not. 

Let’s look at another example:

x is further away than y

This predicate involves two parameters, x and y.  Substituting arguments the sun for x and the moon for y yields a true proposition; substituting arguments the moon for x and the sun for y yields a false one. 
 

The key premise mentions Database Relations.  What, then, is a Database Relation?

The concept of a Database Relation is an elaboration on the concept of a Relation as defined in mathematics.  In mathematics, a Relation is defined as the subset of the Cartesian Product of two or more sets.  (What a Cartesian Product is will be obvious from the example.)  For example, in the sets {John, Charles, Cliff, Dan} and {Leon Trotsky, Genghis Khan}, the Cartesian Product is { (John; Leon Trotsky), (John; Genghis Khan), (Charles; Leon Trotsky), (Charles; Genghis Khan), (Cliff; Leon Trotsky), (Cliff; Genghis Khan), (Dan; Leon Trotsky), (Dan; Genghis Khan)}.  If, now, we pick out a subset of this Cartesian Product by seeing who happens to be standing to the left of whom at the moment, we get this Relation:  { (Charles; Genghis Khan), (Cliff; Genghis Khan), (Dan; Leon Trotsky)}. 

In other words, our Relation is what we get when we start with the predicate:

x is standing to the left of y

and plug in values for x from the set {John, Charles, Cliff, Dan} and values for y {Leon Trotsky, Genghis Khan}, throw away all the false propositions that result, and keep all of the true propositions.

Let me go out on a limb, then, and say that a proposition (remember, our key premise mentions propositions) is a tuple, that is to say, an ordered pair (for example, (Charles, Genghis Khan) ) in a Relation.  (Please, pretty please, don’t saw this limb off.) 

This means then that a proposition is a state of affairs ala R.M. Chisholm.  For example, the proposition Charles is standing to the left of Genghis Khan is the state of affairs comprising the flesh and blood Charles standing to the left of the flesh and blood Genghis Khan.  Propositions as states of affairs are the meaning of sentences… But I digress.

Back to Relations. 

A Database Relation, I have said, is an elaboration of a Mathematical Relation.  A Database Relation comprises a Heading consisting of ordered pairs of (Name Of Type; Type) and a Body consisting in a set of ordered pairs (Name Of Type, Value).  A type is a set, for example, the set of integers, the set of words in a given language, the set of people, the set of cities in the world, and so on.  A value of a type is a member of the set identical with that type.  I will leave name undefined. 

A Database Relation is an abstract object;  it is either an object really existing in some Platonic Heaven someplace or it is a fiction, depending upon which theory of abstract objects is the correct one.  Database Relations form the conceptual skeleton of databases concretely implemented by an RDBMS (Relational Database Management System) functioning inside a physical computer, but at least at the moment I am not talking about physical computers and the software they run.  I am talking about the abstract object, something that has the same status as the number 3 or the isoceles triangle. 

Why do I want to talk about Database Relations rather than Mathematical Relations?  It will be easier in the  posts that (hopefully) will follow to illustrate the Relational Algebra operations Projection and Restriction.  I know how to apply these operations to Database Relations; I am not sure how to apply them to Relations simpliciter.   Projection and Restriction are the Relational Algebra operations which, I claim, will give us a model for sentences such as Joe ate something. 

I’ve laid the groundwork for such a model; now let me go on to produce the model.


The Verb Considered As A Function

From Kroch’s and Santorini’s Syntax of Natural Language:

I embraced the summer dawn

 From the point of view of a simple formal semantics, the verb laugh is a function from entities to truth values, as illustrated in (1). Entities that laugh are associated with the value T(rue); entities that don’t with the value F(alse). In the world described in (1), Beatrice, Gary, Lukas, and Tina laugh, and Chris and Eva don’t.

By convention, entities are indicated by boldface, sets are enclosed in curly brackets, and ordered pairs are enclosed in angle brackets. It is also conventional to indicate denotations of expressions by enclosing the expressions in special square brackets. These special brackets are not part of the HTML character set, so we use two ordinary square brackets instead.
(1) [[ laugh ]] = { Beatrice T,
Chris F,
Eva F,
Gary T,
Lukas T,
Tina T }

Laugh can combine with a single argument, which denotes an entity. Intuitively, we can think of arguments as the central participants in a situation. Combining laugh with an argument (say, Lukas) has a syntactic effect and a corresponding semantic effect. The syntactic effect is to yield the sentence in (2a). (For simplicity, we disregard the past tense morpheme -ed here and in what follows.) The corresponding semantic effect is to apply the function in (1) to the argument; that is, to select the entity denoted by the argument in the function in (1) and to return the associated value. In the example at hand, the sentence comes out as true, as shown in (2b).

(2) a. Lukas laughed.
b. T

On the other hand, combining Chris with laughed yields Chris laughed with a truth value of F.

In addition to denoting simple functions, verbs can also denote recursive functions. For instance, a transitive verb denotes a function from entities to a second function, the latter of the same type as just described for the intransitive verb laugh (a function from entities to truth values). So the transitive verb invite might denote the function in (3).

(3) [[ invite ]] = { Chris Andrew T ) ,
David Andrew T ) ,
Eddie Andrew F ) ,
Chris Brian F ) ,
David Brian F ) ,
Eddie Brian T ) }

Combining invite with a theme argument (say, David) has the syntactic effect of yielding the phrase in (4a). As before, the corresponding semantic effect is to select the entity denoted by the argument in (3) and to return the associated values, as shown in (4b).

(4) a. invited David
b. [[ invited David ]] = { Andrew T ) ,
Brian F ) }

Further combining invited David with an agent argument (say, Andrew) yields the sentence in (5a) and the truth value in (5b). This second step in the derivation of a transitive sentence is exactly equivalent to the first and only step that is necessary in an intransitive sentence.

(5) a. Andrew invited David.
b. [[ Andrew invited David ]] = T

It is important to understand that the order of the arguments in (3) reflects derivational order (the order in which the arguments combine structurally), not their superficial linear order. Given purely semantic considerations, it is equally easy to write functions in which derivational order is congruent with linear order, and you are asked to do so in Exercise 3.1.

Verbs like laugh and invite are instances of one-place and two-place predicates, respectively. The term predicate here refers to a vocabulary item, with a focus on its capacity to combine with one or more arguments. The number of arguments that a predicate requires is its semantic valency.

If truth in hearts that perish

This simple formal semantics is a model of the verb laughs employing abstract objects such as functions, sets, denotations, truth values.  As a function, laughs associates, or is an association of, concrete, flesh-and-blood entity such as Chris or Lukas, with one or another of the abstract objects (T)rue or (F)alse.  Laughs has a parameter which can accept an argument (to use Date’s terminology); or to use the authors’ terminology, laughs can combine with an argument.  When combined with the name Lukas, the function laughs gets applied to the flesh-and-blood Lukas — that is to say, it selects this flesh-and-blood creature — and returns (T)rue.

If one is a Platonist they may be content with treating all the abstract objects mentioned here as existing and non-fictional:  functions and truth values exist as abstract, non-material objects just as abstract objects as the perfect triangle or the perfect square do.  If one is not a Platonist, he may still be content picturing all of these objects as if they existed, and hold out for the hope that there is, or will be, a way of treating all of these as fictions.

When considered as something that can accept (or ‘combine with’) arguments, a function is an abstract machine:  it accepts an input (the name Lukas), performs an ‘applies’ or ‘selects’ operation, and generates an output (here the truth value (T)rue).  The applying and selecting are abstract; that is, no particular, concrete operation is getting specified.  And I suppose this is how one produces an abstract operation:  name an operation, but omit any concrete implementation of that operation. 

Even the Platonist in me, however,  has some difficulty with the notion of abstract operations such as ‘applies’ and ‘selects’.  Tortured by a bee buzzing around in his bonnet, my inner Platonist feels compelled to utilize something like Plato’s Demiurge in the Timaeus to picture these operations.  Instead of Plato’s divine craftsman who shapes the world guided by his vision of the Forms, this Demiurge has something of a lower-level task of taking the string (or sounds, or hand-signals, or whatever) embodying the name Lukas, searching through the entities bearing that name (somehow the Demiurge has no problems with ambiguity), selecting one, seeing that this entity is indeed laughing, and returning a truth value.

This image of a Demiurge selecting entities and applying functions to them would have equal value for the Platonist and the fictionalist, at least if the Platonist hews to Plato.  For Plato regarded regarded his Forms (abstract objects) as real, but his Demiurge as just a myth, just a picture…in other words, a fiction. Likewise, our Demiurge, our all-seeing, untroubled-by-ambiguity selector of entities, is just a picture, a creature existing only in the realm of ‘as if’.  We need this picture as a psychological crutch to make up for that lack of any concrete implementation of the abstract operations which gets the bee in our bonnet buzzing. 

One side-note:  Santorini and Kroch have the function laughs returning both a truth value and a phrase (Lukas laughed).  But isn’t a function supposed to always return just a single value?