The main argument of this book, against a prevailing orthodoxy, is that the study of logic was a vital - and a popular - part of stoic philosophy in the early imperial period. The argument relies primarily on detailed analyses of certain texts in the "Discourses" of Epictetus. It includes some account of logical 'analysis', of 'hypothetical' reasoning, and of 'changing' arguments. Written both for historians and for philosophers, and presupposing no logical expertise, this is an important contribution to the history of philosophy in the early imperial period.