So let’s talk about arguments. No, we’re not going to teach you how to win a fight;
there are other channels for that kind of thing.
But we can talk about the kinds of things sentences need to have inside them in order to express complete
thoughts. Like the story of Goldilocks and the three bears, a sentence can’t be too
big, and it can’t be too small; it needs to be just right.
If sentences have too many or too few words in them, they don’t make sense. To make
sure that the rules of our language create exactly the sentences we need them to, we
need to introduce another tool into our ever expanding kit.
I’m Moti Lieberman, and this is The Ling Space.
So when we first introduced the rules of syntax, we talked about the need for a system that's really flexible.
After all, it has to fit with all kinds of words and sentences, in all kinds
of languages. The framework that we showed you to take care of this was called X-bar Theory.
X-bar theory gives us a general template that we can use for noun phrases, verb phrases,
and everything in between. So, this system is really versatile. But is
it too versatile?
It looks like the X-bar template is so freewheeling, that it’ll create all kinds of
sentences that we might not want it to. So, just from the theory itself, as we’ve
talked about it so far, if we take a sentence like “Goldilocks ate the porridge”, there’s
nothing stopping us from sticking another noun phrase down there at the bottom. Why not have
a sentence like “Goldilocks ate the porridge the soup”? Except that sentence is obviously
pretty bad. It has one too many noun phrases inside of it, and it’s impossible to say
exactly what it means.
Things don’t get much better if we try pruning our tree, either. Take, for example, the sentence
“Goldilocks broke the chair”. If we pluck out “the chair”, we still
get something that fits our X-bar template. The problem is that “Goldilocks broke”
barely qualifies as English, unless Goldilocks is an inanimate object. Or unless she’s
playing pool. Language can get kinda weird at the edges.
So, how do we make sure that the way we formulate our rules doesn’t allow for sentences that
are so full of porridge and soup that they can’t even get out of bed, or sentences
that are over so quickly that you don’t can't find out how the story ends?
Well, we’ll need to add something to our recipe that makes sure that we only get what
we want; no more, and no less.
Based on the examples that we just talked about, you might think that we could just invent some
rule that would say: “make sure that every verb has only one noun phrase after it”. After
all, that would filter out the bad sentences that we’ve seen so far.
But unfortunately, that’s a bit too strict. It might work for sentences with verbs like
“eat” or “break”, but it wouldn't really work for ones with verbs like "sleep".
Not only are we allowed to say “Goldilocks is sleeping”, if we try to add another noun phrase,
like "the bed", we’re back to square one: a sentence that fits our template but that just has no business
at all calling itself English.
It seems like what pieces we want and don’t want in our sentences depends on
what words we start out with. Verbs usually drive the sentential action, and like porridge,
they come in a few different flavors. Some verbs, like “eat” and “break”,
get really lonely unless they’re in the nurturing presence of a noun phrase.
Then we have verbs that are like real party animals, like “give” and “put”,
who aren’t happy unless they have a couple of friends around.
And there are verbs that are so greedy, like “know” and “believe”, that they're not happy
unless you give them a whole other sentence!
We already know that speakers of a language have to pair up each word they have with
some meaning, so it’s not too much of a stretch to suppose that they have to also keep track
of what should show up alongside a verb. You need to make sure that every word in your sentence
is blissfully content, and doing what it’s supposed to.
Speakers just have to remember what a verb needs in order to form a complete sentence and feel
satisfied with its lot in life. Each of these phrases is called an argument. Arguments
come after verbs, but before them, too. A word like “eat” needs two arguments
- specifically, two noun phrases - because there needs to be something that gets eaten,
and someone to do the eating.
“Sleep” only gets one — a noun phrase corresponding to the sleeper.
But something like “put” gets three: two noun phrases and a prepositional phrase,
corresponding to the putter, the thing that gets put and where the thing is put. So
like, The bears put the porridge on the table. Now, okay, so this looks great. But wait,
you think. Just saying that “eat” needs two noun phrases isn’t exactly right. Can
you really say “The porridge ate Goldilocks”?
Not unless it’s some horrible monster gruel that's come to turn this story on its head.
Or, okay, “sleep” needs one NP, so why does “The bed slept” not make
any sense? As it happens, the possibility of sentences
that fit our templates but don’t mean anything was noticed as far back as the mid
1950s by Noam Chomsky. He showed that something could be totally
ok in terms of syntax but just make no sense.
That’s what’s behind maybe the most famous example sentence in all of linguistics: “Colourless
green ideas sleep furiously”.
So we need to go one step further. Verbs can’t just look for any random version of a phrase
to fill in their argument structure. They have certain roles that need to be filled.
Linguists call these theta roles, and they describe the function and meaning of the phrase
in the sentence. So you have roles like AGENT for arguments
that perform some kind of action, or EXPERIENCER for ones that experience some state or emotion.
They can also be things like THEME, for arguments that undergo some action, or GOAL, for the
endpoint of a journey. So, tying it all together, we can say
that a verb like “eat” has two arguments: one AGENT for doing the eating and one THEME for
getting eaten. A verb like “give” looks for three: a
giving AGENT, a GOAL to give the gift to, and a THEME gift.
We’re also left with a nice way to explain why some verbs are content with just one argument, while others
are most happy with two or three. It isn’t totally arbitrary, like “this
verb needs two noun phrases and a prepositional phrase, because grammar”!
Instead, we’ve made a deep connection between the meaning of a verb and the kind of sentence
it appears in.
A verb like “eat” represents an action that really needs both an AGENT (the eater)
and a THEME (something that gets eaten); eating just can’t happen without both of them. And this
fact is encoded in our mental representation of the verbs themselves. That’s how we can make
sure that the verbs get exactly what they need, no more and no less!
Verbs swagger into a sentence looking for a certain number of theta roles, and each
role’s got to be filled by one and only one argument.
And you can’t have arguments just floating around without any theta roles to fill! These two conditions
put together make up what we call the “Theta Criterion”.
And with that in place, we don’t need to worry about crazy sentences sneaking into
our language while nobody’s home.
So, we’ve reached the end of The Ling Space for this week.
If you got out of the house before the bears got home, you learned that X-bar Theory is
a very flexible system that generates far more sentences than we need it to; that verbs
need a specific number of arguments to make sense;
that these arguments can’t just be any old phrase — they need to fill some theta role;
and that the Theta Criterion makes sure that every sentence contains the exact right
number of arguments.
The Ling Space is produced by me, Moti Lieberman and directed by Adèle-Elise Prévost. This
week’s episode was written by Stephan Hurtubise. Our production assistants are him and Georges
Coulombe, our music and sound design is by Shane Turner, and our graphics team is atelierMUSE.
We’re down in the comments below, or you can bring the discussion back over to our
website, where we have some extra materials on this topic.
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