Is grammar dependence real? A comparison between cophonological and indexed constraint approaches to morphologically conditioned phonology

This article compares and contrasts cophonology theory and indexed constraint theory, the dominant current proposals to morphologically conditioned phonology. In cophonology theory, morphologically conditioned phonology is captured by associating each morphological construction or lexical class with its own phonological grammar, or cophonology. All constraints within a given cophonology are purely phonological; no constraint directly refers to morphological context. By contrast, indexed constraint theory assumes a single fixed constraint ranking for the entire language, and captures morphologically conditioned phonology by indexing individual constraints to specific morphological contexts. The article raises three arguments in favor of cophonology theory: greater formal parsimony, the ability to handle free variation, and more accurate predictions about the scope of morphologically conditioned phonological effects. It also evaluates and rejects the primary argument for indexed constraint theory, i.e., Grammar Dependence, the claim that indexed constraint theory is more restrictive in the degree of language-internal diversity allowed. Cophonology theory and indexed constraint theory are equivalent in the range of language-internal diversity they allow; it is argued that the upper limit on language-internal diversity should not be a matter for formal grammar, but instead requires extra-grammatical explanation in terms of the factors influencing language change and variation.