The chapter examines Thucydides’ intellectual milieu, concentrating on medical theories of the time, rhetoric, and especially the rhetorical use of theories of justice and self-interest. It examines the account of the Plague and the impossibility of isolating a cause, akribeia as a wider aim of medical writers, and Thucydides’ familiarity with intellectual theories, which he then supersedes. Finally, it examines aspects of the presentation of rhetoric and its effects: it focuses on Thucydides’ Plataean Debate and the claims made to justice, law, and convention, comparing Antiphon and Thrasymachus’ theories of justice and Thucydides’ possible contribution to this debate.