J. L. Ackrill's work on Plato and Aristotle has had a considerable influence upon ancient philosophical studies in the late twentieth century. In his writings the rigour and clarity of contemporary analytic philosophy are brought to bear upon ancient thought; in many cases he has provided the first analytic treatment of a key issue. Gathered now in this volume are the best of Ackrill's essays on the two greatest philosophers of antiquity. With philosophical acuity and philological expertise he examines a wide range of texts and topics-from ethics and logic to epistemology and metaphysics-which continue to be in the focus of debate.