Unaccusativity is an extended investigation into a set of linguistic phenomena that have received much attention over the last fifteen years. Besides providing extensive support for David Perlmutter's hypothesis that unaccusativity is syntactically represented but semantically determined, this monograph contributes significantly to the development of a theory of lexical semantic representation and to the elucidation of the mapping from lexical semantics to syntax.Perlmutter's Unaccusative Hypothesis proposes that there are two classes of intransitive verbs - unergatives and unaccusatives -...