Voice: Malagasy presents morphologically distinct verbs built from the same root which assign different grammatical cases to DPs with given theta roles, yielding Ss that are theta equivalent, and, with appropriate choice of DPs, logically equivalent, much like active and agented passive Ss in English. The problem is to derive and interpret such Ss so as to yield these judgments of semantic equivalence as theorems. Our solution, which is purely structural, invoking no notion of ‘subject’, ‘topic’, ‘pivot’, ‘trigger’, etc., is (...) simply an explicit syntactic and semantic interpretation of voice affixes. Deriving Ss built from verbs in different voices involves no A movement of DPs. Voice morphology determines the distinctive syntactic and semantic properties of nuclear clauses. This supports that “Variation of language is essentially morphological ...” (Chomsky 1995:7). (shrink)