Does the topic “the categories of being” belong to metaphysics in the “old” sense? A case can be made for saying that it does, based on the fact that Plato's theory of forms (universals, attributes) is a recurrent theme in Aristotle's Metaphysics. In Metaphysics, two of Plato's central theses about the forms come in for vigorous criticism: (i) that things that would, if they existed, be “inactive” (the forms) could be the primary beings, the “most real” things, and (ii) that the attributes of things exist “separately” from the things whose attributes they are. We shall be concerned only with (ii). In the terminology of the Schools, that criticism can be put this way: Plato wrongly believed that universals existed ante res (prior to objects); the correct view is that universals exist in rebus (in objects). It is because this aspect of the problem of universals—whether universals exist ante res or in rebus—is discussed at length in Metaphysics, that a strong case can be made for saying that the problem of universals falls under the old conception of metaphysics. (And the question whether universals, given that they exist at all, exist ante res or in rebus is as controversial in the twenty-first century as it was in the thirteenth century and the fourth century B.C.E.) If we do decide that the problem of universals belongs to metaphysics on the old conception, then, since we have liberalized the old conception by applying to it the contemporary rule that the denial of a metaphysical position is to be regarded as a metaphysical position, we shall have to say that the question whether universals exist at all is a metaphysical question under the old conception—and that nominalism is therefore a metaphysical thesis.