Abstract: The De Interpretatione is one of Aristotle's core works, containing highly influential analyses of the basic elements of language and the nature of truth and falsehood, as well as the famous Sea-battle paradox. As a whole, however, the treatise has been neglected; attention has concentrated on a few oases of interest, and scholars have been satisfied with the medieval view that the treatise is a discussion of the proposition, and forms the second part of the Organon, building on the categories and anticipating the formal logic of the Analytics. This book argues that the subject of the De Interpretatione is not the proposition, as has conventionally been supposed, but the contradictory pair of assertions, and that it is oriented not towards the formal logic of the Analytics, but to the Topics and Sophistic Refutations, the works in which Aristotle describes dialectic, the method of argument consisting in the asking and answering of dialectical questions. In posing a dialectical question, the questioner presents a contradictory pair of assertions and invites the answerer to select one or the other as true, hoping in the end to lead to a refutation, i.e. a proof that the contradictory of the answerer's thesis is true, and therefore the thesis itself is false. The ability to assign assertions to their pairs correctly, and to know in which cases the truth of one member of a pair does not imply the falsehood of the other, are vital tasks for the dialectician. The De Interpretatione's discussion of contradiction thus provides the theoretical background essential for dialectic.

Keywords: ancient philosophy, argument, Aristotle, assertion, contradiction, contradictory, De Interpretatione, dialectic, history of philosophy, logic, paradox, philosophical method, proposition, Whitaker