Minimalist Program - Technical Innovations - Bare Phrase Structure

Bare Phrase Structure

A major development of MP inquiry is Bare Phrase Structure (BPS), a theory of phrase structure (sentence building prior to movement) developed by Noam Chomsky. Interestingly, the introduction of BPS has moved the Chomskyan tradition toward the dependency grammar tradition, which operates with significantly less structure than most phrase structure grammars.

This theory contrasts with X-bar theory, which preceded it, in four important ways:

1. BPS is explicitly derivational. That is, it is built from the bottom up, bit by bit. In contrast, X-Bar Theory is representational—a structure for a given construction is built in one fell swoop, and lexical items are inserted into the structure.
2. BPS does not have a preconceived phrasal structure, while in X-Bar Theory, every phrase has a specifier, a head, and a complement.
3. BPS permits only binary branching, while X-Bar Theory permits both binary and unary branching.
4. BPS does not distinguish between a "head" and a "terminal", while some versions of X-Bar Theory require such a distinction.

BPS incorporates two basic operations: Merge and Move. Although there is active debate on exactly how Move should be formulated, the differences between the current proposals are relatively minute. The following description follows Chomsky's original proposal.

Merge is a function that takes two objects (say α and β) and merges them into an unordered set with a label (either α or β, in this case α). The label identifies the properties of the phrase.

Merge (α, β) → {α, {α, β} }

For example, Merge can operate on the lexical items 'drink' and 'water' to give 'drink water'. Note that the phrase 'drink water' behaves more like the verb 'drink' than like the noun 'water'. That is, wherever we can put the verb 'drink' we can usually put the phrase 'drink water':

I like to _____________ (drink)/(drink water).
(Drinking/Drinking water) __________ is fun.

Furthermore, we typically can't put the phrase 'drink water' in places where we can put the noun 'water':

We can say "There's some water on the table", but not "There's some drink water on the table".

So, we identify the phrase with a label. In the case of 'drink water', the label is 'drink' since the phrase acts as a verb. For simplicity, we call this phrase a verb phrase or VP. Now if we were to Merge 'cold' and 'water' to get 'cold water', then we would have a noun phrase or NP with the label 'water'. The reader can verify that the phrase 'cold water' can appear in the same environments as the noun 'water' in the three test sentences above. So, for 'drink water' we have the following:

Merge (drink, water) → {drink, {drink, water} }

We can represent this in a typical syntax tree as follows:

drink / \ drink water

or, with more technical terms, as:

VP / \ drink water

Merge can also operate on structures already built. If it couldn't, then such a system would predict only two-word utterances to be grammatical. Say we Merge a new head with a previously formed object (a phrase).

Merge (γ, {α, {α, β}}) → {γ, {γ, {α, {α, β}}}}

Here, γ is the label, so we say that γ 'projects' from the label of the head. This corresponds to the following tree structure:

γ / \ γ α / \ α β

Note crucially that Merge operates blindly, projecting labels in all possible combinations. The subcategorization features of the head then license certain label projections and eliminate all derivations with alternate projections.