  Of course, this still leaves us with the question of how in general we are to distinguish genuine relations from the mere significata of relative terms. Here medieval philosophers think that Aristotle’s second definition—which we italicized in the passage quoted above—can be of some help. This definition, as it was commonly interpreted, highlights an important metaphysical or functional role that relations must play: in addition to being signified by relative terms, they are what actually serve to relate two (or more) things—or to put the point in slightly different terms, they are that in virtue of which such things are related. On this interpretation, Aristotle’s definition provides a clear explanation for why heads and hands fail to qualify as genuine relations. Although they are signified by relative terms, they do not relate anything. On the contrary, they are things standing in relations.