Unification and morphological blocking

The paper addresses the question of how ‘Avoid Pronoun’ and similar phenomena can be accommodated in LFG and other unification-based frameworks, considering primarily data from the synthetic vs. analytic verb-subject constructions in Modern Irish, but also data from other languages, including Spanish and English. The solution proposed is a constraint on lexical insertion, the ‘Morphological Blocking Principle’, which is essentially a variant of the Elsewhere Condition, modified to control lexical insertion in LFG. The principle says that if, in a complete sentence structure (comprising both c-structure and f-structure), a lexical item L appears in a c-structure position P corresponding to an f-structure F, and there is another lexical item L' whose specifications are subsumed by those of L but subsume those of F, then the structure is blocked. The principle depends crucially on the use of unification rather than movement to relate the contents of distinct syntactic positions. Discussion is also provided of how the blocking relation can be computed with a reasonable degree of efficiency.I am also indebted to the UMass Amherst linguistics department for providing hospitality and support while some of this work was being done, and also to the Outside Studies Program of the Australian National University.