It is always the conscious or unconscious significance for the future that justifies revenge in the natural course of events; while it is no remedy for my hurt, if some one has put out my eye, to put out his in return, yet this revenge act, and so the feeling which prompts it, is of highest prospective value with reference to future possible enemies. Every one will know that I cannot be harmed with impunity. Despoil or injure the revengeful in any way and you inevitably suffer for it sooner or later, and so revenge acts as a protective psychical variation of high value. On the whole the revengeful is less likely than others to be molested and injured, and thus has a manifest advantage in the struggle for existence. Revenge has, then, also rightfully its own subjective sanction, a pleasure reaction, for revenge is, indeed, “sweet.” Revenge is apparently found in a considerable range in the animal kingdom, and seems universal in the _genus homo_. However, we cannot infallibly conclude from certain actions that revengeful emotion is present, and especially is this so in the case of animals. Thus, in the well-known instance of the elephant, who, observing a man passing by who had greatly annoyed him years before, suddenly drenched him with dirty water, we are not necessarily to suppose that this elephant was prompted by the emotion of revenge; although this may have been the case, we are not perfectly sure how far the elephant did the act merely as recompense for what the man had done, or how far the sight of the injurer, and so one likely to injure, roused to simple anger and defence against the threatening harmful. Many acts which seem like revenge are quite likely to be common defence or offence, are done with reference to what the object is and will be as injurious, based upon knowledge of the past, and not as merely retrospective retributive acts. Memory for injuries received is strong in many animals; that which has harmed is often recognised after many years as the harmful, and appropriate simple emotion, not revenge, is manifested. Rage, rather than revenge, is the usual emotion among lower animals in special instances where revenge might seem called for; and thus it is more likely that the elephant should rage and hate rather than have pure revenge as in the case considered.