 Neither of these property realization relations is the supervenience relation. A property can supervene on other properties even when it is not the kind of property that has a causal role associated with it, as is the case with pure mathematical properties, for instance. Nor is property supervenience required for property realization in either of the above senses. Suppose that F is multiply realizable in that it can be realized by G or realized by H, and that something can be H without being G. Then, despite the fact that G realizes F, two things can differ with respect to F without differing with respect to G in that they both lack G, and so F fails to supervene on G. Of course, F may belong to a family of properties A, and G and H to a family of properties B, such that A-properties supervene on B-properties even though F does not supervene on G in particular.