From The Chronicle of Higher Education:
For many years, I taught an introductory philosophy class based on Plato's Republic. It is a wonderful work through which to bring students to some of the crucial issues that engage and divide human beings—the nature of knowledge, the desirability of democracy, the place of women in society, mathematics, and God. Above all, there is the Theory of Forms, extrasensory entities that are supposed to inform and determine the objects in this world of sensation and experience. They are Plato's answer to the challenge posed by two earlier thinkers: Heraclitus, who claimed that everything changes (“You cannot step into the same river twice.”), and Parmenides, who claimed that nothing changes (“How could what is perish? How could it have come to be?”). The Forms are timeless and yet manifest themselves in this physical world of corruption and decay.
Others intent on the same ends as I was might have chosen different works by Plato, but I suspect that few if any would have seized on Timaeus, a rather odd dialogue (at least to us) in which Plato argues that the world is a giant organism fashioned by a God, the Demiurge. Today it's hard to imagine that in the early Middle Ages, until Thomas Aquinas and others discovered the attractions of Aristotle, Timaeus was the only known work of Plato. And very influential it was, too, as almost everyone in the early centuries of the last millennium agreed that the world was an organism of a kind. Hence, as with all organisms, it was appropriate to think of the world as having sensations and feelings, and also to ask questions about ends and purposes.