It appears to be no very difficult matter to discover causes of war, and indeed a considerable number of causes. In fact the problem seems to yield an embarrassment of riches, especially if our chief interest happens to be a practical one, and we wish to find the causes of war in order to see how they may be controlled. We might even have discovered all the causes of war and still be as far as before from any real understanding of the cause of war. Unless one can know the relative importance of the causes, and the manner in which the causes combine to produce wars; unless the results give in some way a synthetic view of the causes of war, show _dominating_ causes, or reveal a total cause which is not merely a summation of stimuli, but is both a necessary and a sufficient situation for the production of war; unless we have shown some fundamental cause and movement in the social order, we are still left in search of the cause of war. We have, indeed, found a number of causes of war, but at the same time the causes have not appeared to exist as separate causes. We are always catching sight of a movement in the development of nations and of the world--of certain fundamental motives, the most basic of all, the most general, being the motive of power. These causes of war do not appear, however, to be of the nature of a _chain_, giving us the impression that in order to break the habit of war, all we need do is to discover the weakest link in the chain of causes, break the chain there, and so interrupt the whole mechanism of war-making in the world. Above all, although fortuitous events as causes of war must not be overlooked, war is not continually being made anew by the appearance again and again of accidental situations, which are thus to be regarded as the cause of war. War is, first of all, a natural expression of the social life, resting primarily upon the fact of the existence, universally, of groups of individuals acting as units. But here cause and effect are lost in one another. Conflict cements the group, and the existence of the group, again, is the cause of conflict. War is an aspect of the social solidarity of the group acting under certain conditions, and these conditions are the presence of deep desires that can, in general, be satisfied only by the exertion of force on the part of communities acting as wholes.