  The question that realists and nominalists about universals try to answer is: What makes F-things F (where “F” is a sparse property predicate)? For instance, what makes a square thing square? For the realist about universals if something is square, this is in virtue of the thing instantiating the universal squareness. In general, for the realist about universals, things have the sparse properties they do in virtue of instantiating universals.