INTRODUCTION

This chapter investigates Aristotle's application of his theory of natural teleology in the actual explanations he provides in the biological treatises. My discussion draws mainly on the heuristics and explanations Aristotle displays in De Partibus Animalium II–IV, but I complement this account where appropriate or necessary with examples from the other biological treatises.

I shall first, in section 4.1, provide some introductory remarks about the organization of De Partibus Animalium books II–IV and Aristotle's basic heuristic strategies for the formulation of predominantly teleological explanations. In section 4.2, I turn to those cases in books II–IV where Aristotle's usual heuristic strategies prove insufficient and where he engages in a series of inferences building upon the postulation of a teleological principle, such as “nature does nothing in vain,” before or while formulating the actual explanation. I argue that these principles are part of Aristotle's method of discovery and that they function predominantly as heuristic tools for the identification of causally relevant features when these are not immediately discernible. Note that I am not making the claim here that Aristotle's entire theory of natural teleology serves a heuristic function; instead I suggest that his use of teleological principles is best characterized as serving such a function. I take it that the (final) causes these principles help discover are all non-eliminable features of the biological world, which are realized through the goal-directed actions of the formal natures of animals.