 This problem is usually brought out by contrasting it with the general problem of existence of complexes. The question is not “what is it that unifies states of affairs/bundles of tropes?” but rather “what is it that unifies this particular bundle of whiteness, hardness, and sweetness into a lump of sugar?” and “what is that unifies this particular chair and the universal blackness?” Vallicella puts the question, as it applies to facts, in the following way: 