Fear and the predatory impulse, the sexual and display motive, play or the hunting activity as a pleasure for its own sake, with a desire perhaps to practice deception and to exercise intelligence, presumably introduced some kind and degree of definite warfare among primitive groups of men at a very early stage of human life, although of course such a conclusion can be only speculative. Increasing intelligence, the power of discriminating and of reacting to secondary likenesses and differences, and especially the recognition of the nature of death, and the advantages of killing rather than merely overcoming an enemy, the discovery of the use of weapons, introduced warfare into the world. Warfare is, then, not simply the negation of some original principle of mutual aid, nor yet an expression of instinctive aggressiveness or cruelty, but it is a product of original endowment, of conditions of life, and of intelligence all together. It is practical, but at no stage can it be said to be _wholly_ practical. Changes must have taken place in warfare as in other social reactions as men passed through a number of stages from primitive wandering or a relatively unstable life to a stable life, but the motives of conflict cannot have been added to in any essential way. Through all the course of history all the motives that originally made individuals of a group or the groups as wholes antagonistic have remained, although the mental processes have become generalized, fused and transformed. If Gumplowicz is right we can still detect in any great society to-day all the primitive individual and group animosities, tempered down and held in check by laws and customs, but still existent and by no means overcome and made innocuous. These motives of warfare might best be traced out in four more or less definite principles of conduct, or four purposes of war that appear throughout primitive life. These are: 1) thievery, including wife capture; 2) the fear motive; 3) cannibalism; 4) the display motive, with the desire to intimidate and to display power (more or less closely associated with the play motive, the love of hunting, gaming and the dramatic motive).