Isabella Tianzi Cai
Aristotle’s “teleology” is a theory that explains the ends and goals of things or “logos of the telos” (Roochnik 178). Since Aristotle is interested in biology, the best example to illustrate his “teleology” may be the eye. Aristotle thinks that human beings and other animals grow eyes on their bodies not by accident but in order to see. The final cause of the eye is not different from the formal cause of the eye. What the eye is is to see.
However, Aristotle has to defend his “teleology” against those who believe in accidents. He does it by repeatedly referring to plants and animals: “leaves, for instance, grow for the protection of the fruit”; “a swallow makes its nest and a spider its web both naturally and for some end” (199a25). Randomness in organisms is not tolerable in his "teleology" because he believes that “the form is the end, and since everything else is for the end, the form must be what things are for” (199a32). Another problem arises because people often confuse final cause with necessity too. To them, Aristotle argues that “Zeus’s rain does not fall in order to make the grain grow, but of necessity” (198b18). Basically, knowing how rain happens must differ from believing what it rains for. By clarifying the necessity of the seemingly purposeless rain, Aristotle does not destroy his own “teleology.” Instead, he prevents people from extending such a view to all things in nature. In his opinion, the final causes are worth looking for especially for plants and animals.
Aristotle’s defense using plants and animals as examples is not successful because evolutionary scientists today have proven that natural selection, migration, gene drift, and mutation are the four forces of evolution. Both gene drift and mutation are perfect examples of accidents. A favorable trait in a given species of a very small number can possibly disappear after a few generations because of accidental changes in the frequency of certain alleles.

