 Shapiro then points out that this requirement sets up a dilemma for proponents of multiple realizability. Consider what appears to be a genuine case of multiple realizability, that is, two objects that “do the same thing” but in very different ways. Either the realizing kinds genuinely differ in their causally relevant properties or they do not. If they do not, then we don’t really have a case of multiple realizability (like the corkscrews that differ only in color or metal composition). If they do so differ, then they genuinely are different kinds. But then functionally they are not the same kind, and again we don’t have an instance of multiple realizability—of a single functional kind with distinct realizations.