This Companion provides a comprehensive guide to ancient logic. The first part charts its chronological development, focussing especially on the Greek tradition, and discusses its two main systems: Aristotle's logic of terms and the Stoic logic of propositions. The second part explores the key concepts at the heart of the ancient logical systems: truth, definition, terms, propositions, syllogisms, demonstrations, modality and fallacy. The systematic discussion of these concepts allows the reader to engage with some specific logical and exegetical issues and to appreciate their transformations across different philosophical traditions. The intersections between logic, mathematics and rhetoric are also explored. The third part of the volume discusses the reception and influence of ancient logic in the history of philosophy and its significance for philosophy in our own times. Comprehensive coverage, chapters by leading international scholars and a critical overview of the recent literature in the field will make this volume essential for students and scholars of ancient logic. ‘The contributions contained in the three parts of the volume each provide a self-contained presentation of the topic they deal with. As a whole, the contributions in the volume provide a coherent overview of the historical development, thematic focuses and subsequent receptions of ancient Greek logic. The authors demonstrate their excellent knowledge of the respective source material and their ability to provide a correct historical and theoretical assessment and classification without speculation.’ Werner Stelzner, N.T.M A state-of-the-art overview of ancient logic for students and scholars, with in-depth analyses of its central themes. Luca Castagnoli is the Stavros Niarchos Foundation Clarendon Associate Professor in Ancient Greek Philosophy at the University of Oxford, and a Fellow of Oriel College. He is the author of Ancient Self-Refutation (Cambridge, 2010) and the co-editor of Greek Memories: Theories and Practices (Cambridge, 2019). Paolo Fait is the Anthony Quinton Fellow in Classical Philosophy at New College, Oxford. He has published a translation and commentary on Aristotle's Sophistical Refutations (2007) and articles on Aristotle's logic and metaphysics.