The syntactic framework that we talked about before, X' Theory, gives us a very flexible template to build our sentences. The X' template allows us to put different words together in a structured fashion, and to capture the variability in how sentences are ordered in different languages. But just by itself, X' Theory as we've talked about it so far is really too flexible. It can allow sentences that have too many words inside them, or not enough. And clearly, that's something we need to avoid if we want to have a system that really shows how language works.
But we can fix this problem with the introduction of the Theta Criterion. The Theta Criterion has two parts to it. The first part is that every verb has a certain number of arguments to fill. These arguments are the pieces of the sentence that the verb requires to be there for the verb to be used appropriately. Different verbs have different requirements: ones like sleep or jump require only one argument, to be doing the sleeping or jumping, while ones like put or give call for three arguments, to do the giving, get given, and be given to. But whatever the verb's conditions are, they have to be met.
The Theta Criterion also states that every noun in the sentence needs to have a role to play. Once the verb has assigned all of its arguments, you can't just randomly stick in other nouns, too. This is what rules out sentences like Goldilocks ate the porridge the soup. Once eat has filled in its whole argument card, you can't just write in the soup as well. All nouns need a role, and all verbs need their all their required roles to be filled. These conditions keep sentences from being too big or too small, making sure they're just the right size, every time.
In the episode, we talked about the players that take part in the action represented by a verb, and we introduced the Theta Criterion to make sure they find their way into a sentence (and to make sure things don’t get too crowded). But, you might have noticed that we can stuff a lot into a sentence that goes far beyond a verb’s bare essentials. Have a look at the sentence in (1).
(1) Goldilocks carefully sipped the hot porridge.
You’ll notice that we’ve qualified the verb with the adverb “carefully”, which gives us a little extra bit of detail about how the action was performed. We’ve also described the porridge a little, using an adjective to assign it a temperature. Unlike our arguments — the noun phrases “Goldilocks” and “the porridge” — these words don’t need to be there; they’re just providing the sentence with some extra company. But they can leave, and everything still works; just have a look at (2).
(2) Goldilocks sipped the porridge.
This sentence carries the same basic meaning as (1), just without the particulars. Things only go awry when we try to cut out an argument, as in (3), where the asterisk indicates unnaturalness.
(3) *Goldilocks sipped.
While this phrase certainly has some kind of meaning, it can’t stand on its own. It isn’t something that describes an entire event, and it doesn’t have a truth value, meaning that it can’t be said to be true or false in any meaningful way. Arguments are just too important to be left out so casually. To distinguish the words we need from the ones we don’t, we can refer to the class of optional elements as “modifiers”.
Complicating things further, we can’t really predict whether a phrase will be an argument or a modifier based on its category. We can sneak a modifying noun phrase into a sentence, as long as we dress it up right. In (4), we’ve included an optional instrument — a spoon — by embedding it inside a prepositional phrase.
(4) Goldilocks sipped the porridge with a spoon.
Yet, prepositional phrases can be arguments too, as seen in (5). In this case, we might name the theta role that this PP receives LOCATION, or maybe GOAL. And we know it needs a theta role, because the verb just can’t function without it, as in (6).
(5) The bears put the porridge on the table.
(6) * The bears put the porridge.
Entire sentences can bear theta roles, as we can see in (7), where the phrase that follows the verb “know” must be present to fill the role of an EVENT or PROPOSITION — that is, something that happened, and that can either be true or false.
(7) Goldilocks knew that nobody was home.
Of course, even sentences can be modifiers, as in (8), where one serves as a kind of causal explanation for the main sentence.
(8) Because nobody was home, Goldilocks took a nap.
Now, since category seems not to play too much of a role in determining whether a phrase is an argument or a modifier, you might be wondering how we represent the difference syntactically. The answer lies in the tree below!
Notice that the verb’s THEME is right next to it; that is, the NP “the hot porridge” resides at the very same ‘height’ as the verb, and branches out of the very same node as the verb. Thus, the THEME argument occupies what is known as the complement position within the verb phrase. Complements have the honour of hanging out right beside the words that give a phrase its category (e.g., the verb inside a VP, or the noun inside an NP).
On the other hand, modifiers occupy different sorts of positions within a sentence; they don’t get to cozy up to verbs and nouns, and are instead relegated to less privileged positions beside V’ nodes and N’ nodes. We call these less desirable spots within a tree adjunct positions.
So, arguments are generally complements and modifiers are generally adjuncts. So what? You might ask us why we should bother making the distinction at all. Well, it’s because the contrast we’ve presented to you here draws a significant amount of empirical support. Have a look at what happens when we make a replacement in the verb phrase that doesn’t target the modifier carefully, leaving it behind.
(9) Goldilocks had carefully done so.
Everything turns out okay, because modifiers are adjuncts, and are far enough away from what they modify to remain calm when left alone. Arguments, on the other hand, tend to panic.
(10) * Goldilocks had carefully done so the hot porridge.
Replacing only the verb and leaving the THEME argument behind doesn’t work out very well in this sentence. This is because arguments, being complements, are too attached to the verb to be left behind, and just freak out and ruin the whole sentence.
So, the idea of arguments presented here and in the episode ends up describing not only a semantic notion, but a syntactic one as well. Arguments seem to behave differently from modifiers, and so we afford the two of them distinct positions within a tree, which ties nicely into our proposal that the meaning of a sentence is very closely tied to its structure.
So how about it? What do you all think? Let us know below, and we’ll be happy to talk with you about arguments, how best to fit them in the structure, and constructing different kinds of meanings. There’s a lot of interesting stuff to say, and we want to hear what interests you!