When we think of the problem of ‘universals’, we tend first of all to identify this issue with medieval philosophy. In that period the arguments ran hot and heavy, and the result was that philosophers almost came to be classified according to the position each took about the relation between the individual and universal concepts. Of course, the fact is that the problem of universals has been important in every philosophical age in western thought. Metaphysics as an enterprise may rise and fall in popularity, but the problem of universals is always with us. Yet, like most philosophical problems of importance, it has not always meant one thing.