This revision of Whitaker's 1993 Cambridge doctoral thesis is the only book-length treatment of Aristotle's De interpretatione in English. The writing is exceptionally clear, and the exposition procedes chapter by chapter. Whitaker's main thesis is that the De interpretatione is primarily about the relations that can exist between contradictory assertions such as "Socrates is sitting" / "Socrates is not sitting". Thus he does not view the treatise as one primarily about linguistics or metaphysics, as has sometimes been maintained. Most interesting is his treatment of chapters 7, 8, and 9, where Aristotle discusses exceptions to the rule that, in any pair of contradictory assertions, one must be true and the other false. Chapter 9, on Whitaker's view, thus argues that future contingent assertions present an exception to this rule, and not an exception to the Principle of Bivalence. Although Whitaker's treatment of the famous sea-battle chapter is somewhat thin, it is a novel and interesting interpretation. Overall the book is an extremely valuable contribution to Aristotelian studies, and it ought to be read by anyone interested in the history of logic, philosophy of language, or Aristotle's rhetoric and dialectic.