This study offers a comprehensive new interpretation of one of Plato's most enigmatic and controversial dialogues, the Cratylus, showing it to present a complex and unified argument for a positive conclusion. The key to understanding this argument is to see that the Cratylus, Plato's most extended discussion of language, is essentially a normative inquiry, to be interpreted alongside his ethical and political works: it seeks to determine what deserves the name 'name', much as the Statesman determines who should count as a statesman. Thus Plato's starting-point is the principle that the correctness of names is a matter of 'nature'. The alternative 'conventionalist' theory is discussed to clear the way for this inquiry: by refuting conventionalism. Plato undermines the commonsensical assumption that all socially accepted names are 'correct', an assumption which would preclude his radical normative project. By the end of the dialogue, however, Plato's project turns out to have a paradoxical and pessimistic result: for names are found to be a kind of imitation, and as such incapable of real correctness. The book argues that this position is retained by Plato, against the common view that this discussion of syntax in the Sophist represents a significant departure from the Cratylus. Throughout, the book combines analysis of Plato's arguments with attentiveness to his political method, including its 'dramatic' or 'literary' features; in particular, Socrates' extended etymological discourse long an interpretive puzzle, is explained in terms of the various Platonic genres to which it belongs.