Specifiers, Not Heads, Determine Phrase and Clause Type

The idea that the head of an expression determines the type of that expression is a deeply entrenched axiom of modern linguistics. It is the basis of X-Bar Theory and Dependency Grammar and a key notion underlying Head Driven Phrase Structure Grammar (HPSG) and Generalized Phrase Structure Grammar (GPSG). It has a long history dating back at least to Bloomfield’s notion of endocentric constructions. There are only a few criticisms of this important axiom. Very different linguistic theories accept it as central (e.g. Minimalist Program and Transformational Grammar, Dependency Grammar, HPSG and to a lesser extent GPSG). Despite the wide acceptance of this axiom within modern linguistics, it is argued in this paper that specifiers, not heads, determine the grammatical type of expressions in which they occur. After considering the evidence for treating specifiers as the phrase and clause type determining elements, some theoretical and computational ramifications of this position will be considered.