The Physica forms Aristotle's most fundamental treatise in his studies of natural science. In this treatise, Aristotle investigates the principles and causes of all things that have a nature – that is, of all things that have an internal principle of change and rest – with the purpose of generating knowledge of natural phenomena (Ph I.1, 184a10–16). In the course of doing so, Aristotle defines a large number of key notions of his natural philosophy, such as motion and change, space and time, matter and form, causal explanation, luck and spontaneity, teleology and necessity. The conceptual apparatus and framework laid out in the Physica are consequently applied and reshaped for the inquiries into the more specific and more complex segments of the natural world, written down in Aristotle's other natural treatises.
Final causes and natural teleology figure especially prominently in the second book of the Physica, where Aristotle defines his concept of nature, introduces his theory of four types of cause or causal explanation, and discusses the kinds of cause operative in art and nature. In this chapter, I shall focus on Aristotle's first argument in defense of natural teleology against his materialist predecessors (in Ph II.8, 198b16–199a8), which raises an important aporia about the role of teleology, necessity, and chance in the proper explanation of natural phenomena. The main purpose of this chapter is to provide an interpretation of this argument, which will build upon a distinction I draw between primary and secondary types of teleology.