Sophists and rhetoricians like Gorgias are often accused of disregarding truth and rationality: their speeches seem to aim only at effective persuasion, and be constrained by nothing but persuasiveness itself. In his extant texts Gorgias claims that language does not represent external objects or communicate internal states, but merely generates behavioural responses in people. It has been argued that this perspective erodes the possibility of rationally assessing speeches by making persuasiveness the only norm, and persuasive power the only virtue, of speech. Against this view, I show how Gorgias’ texts support a robust normativity of language that goes well beyond persuasion while remaining non-representational. Gorgias’ claims that a speech can be persuasive and false, or true and unpersuasive, reveal pragmatic, epistemic, and agonistic constraints on the validity of speech that are neither representational nor reducible to sheer persuasiveness.