Abstract

Aquinas consistently criticizes Plato and his followers for their commitment to the existence of separate forms or ideas. There is no whiteness existing by itself apart from any particular white things or any particular person's thoughts about them. The same goes for every natural form, from humanity to heat. And yet Aquinas is happy to appeal to such separate forms as examples to illustrate his own metaphysical views. This seems like a strange and dangerous procedure. If Aquinas considers Platonic forms to be incoherent, then surely their incoherence will infect the notions he uses them to illustrate. But does Aquinas consider Platonic forms to be incoherent? I don't think so. The very fact that he uses them as examples to illustrate his own views suggests otherwise. And at one point Aquinas even grants that God could create a Platonic form such as a separate whiteness. Why, then, does he reject such forms? What has Aquinas got against them? An examination of his main critical discussions of Platonic forms shows that he rejects them not because he thinks they are impossible, but because he thinks they are unnecessary. In other words, Aquinas rejects Platonic forms on grounds of parsimony, since he thinks they cannot explain any of the things that Plato posited them to explain, such as the changes things undergo, the nature and existence of things, and our knowledge of them. Where Plato's separate forms fail, however, Aquinas thinks Aristotle's inherent forms succeed.