The paper will explain the significant contribution that Thucydides’ Mytilenean Debate makes to our understanding of fifth-century rhetoric and its representation: firstly, by vindicating Thucydides’ controversial methodology in his representation of speeches, of which this debate is paradigmatic; secondly, by illustrating the influence that the tradition of model forensic speeches had on these deliberative ones in form and content (i.e. arguments); and thirdly, by demonstrating the ambiguity of rhetoric’s dangerously powerful role in the political decision-making in Athens.