The method of dialectic occupies an ambiguous yet central position in Islamic philosophy and the sciences. This study examines Aristotle's treatise dedicated to dialectic, his Topics, in the works of two influential thinkers of Arabic philosophy: al-Fārābī (d. 950-951 CE) and Avicenna (d. 1037 CE). The study aims to show the systematic place of dialectic (jadal in Arabic) in their works and its relationship to the method of scientific proof, ethics and political philosophy. As this study shows, both thinkers develop their key concepts and theories of dialectic in response to the Greek commentary tradition, in particular Alexander of Aphrodisias (c. 200 CE) and Themistius (d. c. 387 CE). In addition to the Greek commentators, theories of dialectical argumentation within the Islamic sciences also exerted a great influence on the authors studied. Philosophical dialectic was not least a rival project to the dialectic of theologians and legal scholars. This book is intended not only for those interested in Ancient and Arabic philosophy, but also in Islamic theology and jurisprudence.