A dualist syntax has two components: (1) the lexicon, a structured set of formatives ('words'); and (2) rules for combining those formatives into utterances. This paper defends syntactic dualism against three 'monist' challenges. First, evidence for lexical argument structure can be found in deverbal nominalization, which preserves that structure systematically. Second, words represent the smallest units for idiom formation and contextual polysemy effects, which is expected on the dualist view but not if word meanings are composed in the syntax. Third, the count/mass properties of nouns suggest an interleaving of conceptual and grammatical information in semantic composition.