“We repeatedly find that in his discussions about knowledge Plato just assumes or asserts that the Ideas exist, and then explains what "knowledge" is (for example, Rep. 476a ff., 507a-b ff., 596a and context, Pho. 100b ff.). We do not seem to get an account of how we know these ontological assumptions to be true. Indeed, one is justified in wondering whether Plato has a "theory" of Ideas at all.”