The DP Hypothesis—a case study of a sticky idea

Recently, in service of a course I’m teaching, I had a chance to revisit and fully engage with what might be the stickiest idea in generative syntax—The DP hypothesis. For those of you who aren’t linguists, the DP hypothesis, though highly technical, is fairly simple to get the gist of based on a couple of observations:

Observation 1: Words in sentences naturally cluster together into phrases like “the toys”, “to the store”, or “eat an apple.”

Observation 2: In every phrase, there is a single main word called the head of the phrase. So, for instance, the head of the phrase “eat an apple” is the verb “eat.”

These observations are formalized in syntactic theory, so that “eat an apple” is labeled a VP (Verb Phrase), while “to the store” is a PP (Preposition Phrase). Which leads us to the DP hypothesis: Phrases like “the toys,” “a red phone,” or “my dog” should be labelled as DPs (Determiner Phrases) because their heads are “the,” “a,” and “my,” which are called determiners in modern generative syntax.

This is fairly counterintuitive, to say the least. The intuitive hypothesis—the one that pretty much every linguist accepted until the 1980s—is that those phrases are NPs (Noun Phrases), but if we only accepted intuitive proposals, there’d be no science to speak of. Indeed, the all the good scientific theories start off counterintuitive and become intuitive only by force of argument. One of the joys of theory is experiencing that shift of mind-set—it can feel like magic when done right.

So it was quite unnerving when I started reading the actual arguments for the DP hypothesis, which I had, at one point, fully bought into, and and began to become less convinced by each one. It didn’t feel like magic, it felt like a con.

My source for this is a handbook chapter by Judy Bernstein that summarizes the basic argument for the DP Hypothesis—a twofold argument consisting of a Parallelism argument and purported direct evidence of the DP Hypothesis— as previously advanced sand developed by Szabolcsi, Abney, Longobardi, Kayne, Bernstein herself, and others.

The parallelism argument is based on another counterintuitive theory developed in in the mid-20th century which states that clauses, previously considered either headless or VPs, are actually headed by abstract (i.e., silent) words. That is, they are variously considered TPs (Tense Phrases), IP’s (Inflection Phrases), or CPs (Complementizer Phrases). The parallelism argument states that “if clauses are like that, then ‘noun phrases’ be like that too” and then finds data where “noun phrases” look like clauses in some way. This might seem reasonable on its face, but it’s a complete non sequitur. Maybe the structure of a “noun phrase” parallels that of a clause, but maybe it doesn’t. In fact, there’s probably good reason to think that the structure of “noun phrases” is the inverse of the structure of the clause—the clause “projects” from the verb, and verbs and nouns are complementary, so shouldn’t the noun have complementary properties to the verb?

Following through on parallelism, if extended VPs are actually CPs, then extended NPs are DPs. Once you have that hypothesis, you can start making “predictions” and checking if the data supports them. And of course there is data that becomes easy to explain once we have the DP Hypothesis. Again, this is good as far as it goes, but there’s a key word missing—”only.” We need data that only becomes easy to explain once we have the DP Hypothesis. And while I don’t have competing analyses for the data adduced for the DP Hypothesis at the ready—though Ben Bruening has one for at least one such phenomenon—I’m not really convinced that none exist.

And that’s the foundation of the DP Hypothesis, a weak argument resting on another weak argument. Yet, it’s a sticky one—I can count on one hand the contemporary generative syntacticians that have expressed skepticism about it. Why is it so sticky? My hypothesis is that it’s useful as a shibboleth and as a “project pump”.

Its usefulness as a shibboleth is fairly straightforward—there’s no quicker way to mark yourself as a generative syntactician than to put DPs in your tree diagrams. Even I find it jarring to see NPs in trees.

To see the utility of the DP Hypothesis as a “project pump”, one need only to look at the Cartography/Nanosyntax literature. Once you open up a space for invisible functional heads between N and D, you seem to find them everywhere. This, I think, is what Chomsky meant when he described the DP Hypothesis as “…very fruitful, leading to a lot of interesting
work” before saying “I’ve never really been convinced by it.” Who cares if it’s correct, it contains infinite dissertations!

Now maybe I’m being to hard on the DP and its fans. After all, as far as theoretical avenues go, the DP Hypothesis is something of a cul de sac, albeit a large one—the core theory doesn’t really care whether “the bee” is a DP or and NP, so what’s the harm? I could point out that by maiking such a feeble hypothesis our standard, we’ve opened ourselves to being dunked on my anti-generativists. Or I could bore you with such Romantic notions as “calling all things by their right names.” Instead, I’ll be practical and point out that, contrary to contemporary digital wisdom, the world is not infinite, and every bit of real estate given to the DP cul-de-sac in the form of journal articles, conference presentations, tenure-track hires, etc. is space that could be used otherwise. And, to torture the metaphor further, shouldn’t we try to use our real estate for work with a stronger foundation?