ABSTRACT
A key guiding assumption in anatomy and physiology, from ancient times through the scientific revolution, was the idea that nature exhibited purpose. Plato (c. 427-347 B.C.) and Aristotle (384-322 B.C.) addressed the question of the origin of the universe in different ways, but both included purpose in their explanations. Plato rejected a chance beginning of the universe and intuited that the Demiurge (Divine Craftsman) had made the cosmos according to design. The idea of a designed universe leads directly to the concept of purpose in nature. Purpose is different from function or description. The diagram of a clock gives the plan of its workings, and, while an explanation of how each part functions may exist, the designed purpose, the reason for which the clock exists, is to tell time. Plato’s approach to science, besides explaining how nature operated, also asked why it functioned in the way it did.
