THE X - BAR THEORY OF PHRASE STRUCTUREAndr

X-bar theory is widely regarded as a substantive theory of phrase structure properties in natural languages. In this paper we will demonstrate that a formalization of its content reveals very little substance in its claims. We state and discuss six conditions that encapsulate the claims of X-bar theory: Lexicality | each nonterminal is a projection of a preterminal; Succession | each X n+1 dominates an X n for all n 0; Uniformity | all maximal projections have the same bar-level; Maximality | all non-heads are maximal projections; Centrality | the start symbol is a maximal projection; and Optionality | all and only non-heads are optional. We then consider recent proposals tòeliminate' base components from transformational grammars and to reinterpret X-bar theory as a set of universal constraints holding for all languages at D-structure, arguing that this strategy fails. We show that, as constraints on phrase structure rule systems, the X-bar conditions have hardly any eeect on the descriptive power of grammars, and that the principles with the most chance of making some descriptive diierence are the least adhered to in practice. Finally, we reconstruct X-bar theory in a way that makes no reference to the notion of bar-level but instead makes the notion`head of' the central one. 1 1. Introduction. The aim of this paper is to undertake a systematic examination of the content of X-bar theory and its consequences for language description. The topic is truly central to modern grammatical theory. X-bar theory is discussed in almost all modern textbooks of syntax, and it is routinely assumed as a theory of phrase structure in a variety of otherwise widely diiering schools of grammatical thought such as government-binding theory (GB), lexical-functional grammar (LFG), and generalized phrase structure grammar (GPSG). 1 One of the primary tasks of syntactic theory is to explain how sentences are built from words. This explanation is generally conceived of in terms of assigning syntactic structures to sentences. The exact form and content of the structures that should be assigned has been strongly debated, but there is overwhelming agreement that constituency information is a crucial element in any adequate analysis of sentential structure. However, there is very little agreement among syntacticians concerning the phrase structure of even the simplest sentences. Questions concerning the exact labeling and bracketing of the constituents in such sentences as Mary will have been swimming (what is the constituency of the auxiliary and …