Aristotle’s conception of change as being a process of something coming to be out of its opposite is troubling and does not sit well with his conception of the four causes. The idea gains strength from instances of change between binary opposites. For example, for something to become hot, it must have been colder before, so we can say that heat comes to be from out of its opposite, cold. However, there are many examples of change that do not mediate between binary opposites. In the summary just presented, we used the example of building a house when discussing the four causes. Aristotle might argue that the house comes to be from out of its opposite, which is “not a house,” but this is unconvincing. A house comes to be from out of a pile of bricks, wood, and mortar, and it seems far-fetched to argue that a pile of bricks, wood, and mortar are the opposite of a house. That same pile of bricks, wood, and mortar could be used to build many different kinds of structure, so Aristotle would have to say that the same pile of bricks, wood, and mortar is the opposite of an infinite number of possible buildings.

In his treatment of final causes, Aristotle boldly asserts that all of nature is teleological, meaning that it is organized toward a final end. In other words, he believes that all natural things have not only form and matter but also purpose. This belief in teleology deeply informs all of Aristotle’s work, from his scientific writings to his ethics. This belief also clashes sharply with modern conceptions of science, which explicitly does not try to identify purpose in the processes it observes. Aristotle’s conception of teleology in nature comes primarily from his impression of biological organisms, all of which are complex and highly efficient. Such organisms could not possibly come into being at random, he reasons, and so must all be designed with a particular purpose. It is interesting to note that, in arguing for this conclusion, Aristotle rejects an evolutionary conception of nature as advanced by Empedocles. Empedocles did not have the understanding of genetics or speciation that make modern evolutionary biology coherent, so Aristotle’s attack on Empedocles is valid. This fact may lead us to wonder, however, whether we might have developed modern evolutionary biology sooner than the nineteenth century had Aristotle not convinced his peers that Empedocles’ views were mistaken.