INTRODUCTION

Aristotle's theory of natural teleology applies in particular to living natural substances: their coming to be and existence, their change and development, and many of their differentiations are the result of the goal-directed actions of their formal natures. In the following two chapters, I discuss the role of teleology in the explanations Aristotle provides of the presence, absence, and differentiations of animal parts in De Partibus Animalium.

In Chapter 4, I shall present an analysis of the structure, role, and explanatory of force of the actual explanations recorded in De Partibus Animalium books II–IV; here, in Chapter 3, I shall first outline Aristotle's theory of explanation in biology as introduced in De Partibus Animalium book I. In section 3.1, I sketch the demonstrative character of the science of biology; this will provide some background to the larger scientific context within which Aristotle's use of teleological explanations takes place. In section 3.2, I discuss the notions of teleology that Aristotle employs in his discussion of the standards for explanation in the natural sciences in De Partibus Animalium book I. My aim here is to show that there are two types of teleology underlying these explanations: a primary kind that involves formal natures realizing a preexisting potential for form through conditional necessity, and a secondary kind that involves formal natures using materials that have come to be of material necessity for something good.