In this introduction to the first installment of the Common Knowledge symposium on xenophilia, the editor explains the rationale of the new project, citing increases in aggressive xenophobia internationally. He comments on the intergroup-relations theorist Todd Pittinsky's argument that, since tolerance is not logically the antithesis of negative feelings toward out-groups, even long-established traditions of toleration are inadequate to prevent intergroup aggression. Pittinsky proposes that tolerance be replaced, as a principle of peacekeeping, by the encouragement of positive feelings toward out-groups, and the author of this essay responds by showing how the Freudian theory of ambivalence and the history of literature on which Freud drew in constructing it support Pittinsky's viewpoint. Enemies regularly fall in love, above all in Shakespearean drama, which Freud explains by arguing that all human relations are love-hate relations. Thus, this essay suggests, it takes as much psychic energy to repress the love in what appear to be relationships of hatred as to repress the hatred in what appear to be relationships of love. There is a metaphysical component as well to this argument: the xenophobe and xenophile equally presuppose that the identity principle (a = a) is applicable to society as well as to mathematics; both assume that each discrete social group is self-identical and differs from all other groups more or less radically. The main difference between –phile and –phobe is the latter's relative incapacity to live with ambivalence. Given these arguments, one must expect to find negative as well as positive motives in the etiology and conduct of xenophilia—and the first installment of the Common Knowledge symposium is said to focus on cases of xenophilia in which varieties of enmity accompany that singular and underrated variety of love.