Not all features of a car contribute to efficient transportation—some features are added for esthetic or other reasons. But as long as a feature is added because it exhibits certain properties—such as appeal to the esthetic preferences of potential customers—it may be explained teleologically. Nevertheless, there may be features in a car, a knife, or any other man-made object that need not be explained teleologically.

That knives have handles may be explained teleologically, but the fact that a particular handle is made of pine rather than oak might simply be due to the availability of material. Similarly, not all features of organisms have teleological explanations.