Aristotle’s ἔνδοξα: Authority and dialectic in ancient science and philosophy. The focus of this first book-length study on Aristotle’s notion of endoxa is the use and theory of authority and acceptable premisses in argument. In Aristotle’s works, reviews of reputed philosophers, the “wise”, but – interestingly – also “what all think” and “what seems true to the majority” play a prominent role. Aristotle calls such views endoxa, “reputable” or (as I argue) “acceptable” opinions. In the first book of the Metaphysics, for example, he famously cites the views of philosophical predecessors to show that his four types of cause cover all styles of inquiry. In Aristotle's Ethics, criticism of the “wise” such as Socrates serves as the point of departure for Aristotle's own arguments, in which deference to majority opinion and the consensus omnium are conspicuous. But why should what people think be important for inquiries into the truth of the matter, either in the theory of motion, the question of weakness of will, or the study of what exists and the manifold causes of things? This book elicits answers from Aristotle on these questions.