Aristotle's biological works - constituting over 25% of his surviving corpus and for centuries largely unstudied by philosophically oriented scholars - have been the subject of an increasing amount of attention of late. This collection brings together some of the best work that has been done in this area, with the aim of exhibiting the contribution that close study of these treatises can make to the understanding of Aristotle's philosophy. The book is divided into four parts, each with an introduction which places its essays in relation to each other and to the wider issues of the book as a whole. The first part is an overview of the relationship of Aristotle's biology to his philosophy; the other three each concentrate on a set of issues central to Aristotelian study - definition and demonstration; teleology and necessity in nature; and metaph themes such as the unity of matter and form and the nature of substance.