Aristotle's Posterior Analytics elaborates for the first time in the history of Western philosophy the notions of science and the requirements for the distinctive kind of knowledge scientists possess. His model is mathematics and his treatment of science amounts to a philosophical discussion, from the perspective of Aristotelian syllogistic, of mathematical proofs and the principles they are based on. Chapters 1-8 expound the foundations of Aristotle's theory, pointing out the similarities and differences between scientific knowledge and other types of knowledge, establishing the need for basic principles, and identifying the types of principles and the source of necessity associated with scientific facts. Philoponus' massive commentary, the most complete ancient discussion of Posterior Analytics Book 1, offers uniquely valuable testimony to the way this book was read and understood in late antiquity, as well as providing information on earlier interpretations. Of particular interest is Philoponus' account of scientific principles, which is based not only on Aristotle but also on the Greek mathematical tradition, especially Euclid and his commentator Proclus. Inna Kupreeva is Lecturer in Philosophy, University of Edinburgh. Richard Sorabji is Research Professor of Philosophy at King's College London and a Fellow of Wolfson College, Oxford, UK. He is the author of many books, including Necessity, Clause and Blame , Matter, Space and Motion , and Time, Creation and the Continuum , all published by Bloomsbury, and general editor of the Ancient Commentators on Aristotle series. Richard McKirahan is the Edwin Clarence Norton Professor of Classics and Professor of Philosophy at Pomona College, Claremont, California, USA. His publications include Cicero, De Natura Deorum, Book I (1997), A PreSocratics Reader (1996) and Readings in Ancient Greek Philosophy (1995). Michael Griffin is Professor of Classics and Philosophy at the University of British Columbia, Vancouver, Canada. He is co-editor of the series Ancient Commentators on Aristotle and translator of two of its volumes: Olympiodorus: Life of Plato and On Plato First Alcibiades 1–9 (Bloomsbury 2014) and Olympiodorus: On Plato First Alcibiades 10–28 (Bloomsbury 2015).