As to the details of the study of war--we first of all consider the origin and the biological aspects of war; then war as related to the development, in the social life and in the life of the individual, of the motive of power. The instincts that are most concerned in the development of this motive of power are then considered, and also the relations of war to the aesthetic impulses and to art. Nationalism, national honor and patriotism are studied as causes of war. The various "causes" that are brought forward as the principles fought for are examined; also the philosophical influences, the moral and religious motives and the institutional factors among the motives of war. Finally the economic and political motives and the historical causes are considered. The conclusion is reached that the motive of power, as the fundamental principle of behavior at the higher levels, is the principle of war, but that in so general a form it goes but a little way toward being an explanation of war. We find the real causes of war by tracing out the development of this motive of power as it appears in what we call the "intoxication impulse," and in the idea of national honor and in the political motives of war. It is in these aspects of national life that we find the motives of war as they may be considered as a practical problem. But we find no separate causes, and we do not find a chain of causes that might be broken somewhere and thus war be once for all eliminated. Wars are products of the whole character of nations, so to speak, and it is national character that must be considered in any practical study of war. It is by the development of the character of nations in a natural process, or by the education of national character, that war will be made to give way to perpetual peace, if such a state ever comes, rather than by a political readjustment or by legal enactments, however necessary as beginnings or makeshifts these legal and political changes may be.