History shows that we must accept hatred as an underlying cause of war. The reaction of deep anger which may be aroused by a variety of situations that arise among nations, especially when it is, so to speak, an outbreak of a long continued hatred, is a proximate cause of wars. Hatred, the reaction of anger prolonged into a mood, differs as national or group emotion from the anger of the individual in part by being subject strongly to group suggestion, and in part because in the group consciousness there is only rarely a means of expression, on the part of the individuals of the group, of the feelings of hatred. Enemies are far away and inaccessible. Therefore hatred may become deep and chronic. Hatred between nations is usually based upon a long series of reprisals and a history of invasions. These invasions are primarily physical invasions, but later invasions in the sphere of invisible values, offenses to honor and the like are added. These ideal values come to be regarded as more vital than material values. Hatred between groups becomes chronic and often seems to be groundless because the values concerned have thus become intangible. The chronic moods of hatred and dislike become explosive forces, ready to be excited to action whenever any difference arises. Veblen (97) says wars never occur except when questions of honor are involved, which is of course equivalent to saying that the reaction of anger is always required as an immediate cause of war. Veblen maintains also that emulation is always involved in the patriotic spirit, that patriotism always contains the idea of the defeat of an opponent, and is based upon collective malevolence. The range of these occasions of crisis is so great, and the feelings of hatred so persistent and volatile, that the mechanism for the production of war is always present. These causes range all the way from violation of property to offense to the most abstract ideas of national etiquette. Violation of international law, of moral principles, we see now, may have very far-reaching effects as infringing the sphere of honor of nations not directly concerned, since the prestige of all nations as participants in creating law and becoming upholders of it is affected.