Aristotle is a rarity in the history of philosophy and science - he is a towering figure in the history of both disciplines. Moreover, he devoted a great deal of philosophical attention to the nature of scientific knowledge. How then do his philosophical reflections on scientific knowledge impact his actual scientific inquiries? In this book James Lennox sets out to answer this question. He argues that Aristotle has a richly normative view of scientific inquiry, and that those norms are of two kinds: a general, question-guided framework applicable to all scientific inquiries, and domain-specific norms reflecting differences in the target of inquiry and in the means of observation available to researchers. To see these norms of inquiry in action, the second half of this book examines Aristotle's investigations of animals, the soul, material compounds, the motions of heavenly bodies, and respiration.