Bertrand Russell, in answer to the question, "Why do men fight?" which is the title of his book dealing with the causes of war, says, in substance, that men fight because they are controlled by instinct (and also by authority), rather than by reason. Men will cease fighting when reason controls instinct, and men think for themselves rather than allow their thinking to be done for them. This view does not explicitly state that war is a reversion, for man may be at no point better or more advanced than a creature of instinct, but it lays the blame for war upon the original nature of man. Man has instincts which presumably he has brought with him from his pre-human stage, and some of these instincts are, on their motor side, the reactions of fighting. Le Bon (42) speaks of a conscious and an unconscious will in nations, and says that the motives behind great national movements may be beneath all conscious intentions, and may anticipate them. The Englishman in particular lives, in a sense, a divided life, since there is a manifest inconsistency between what he really is and what he thinks. What these instincts are, Le Bon does not specify; presumably they may be either better or worse than the conscious motives. Trotter (82) and also Murray (90) consider war from a biological standpoint, regarding it as a herd phenomenon. Trotter's view, especially his interpretation of Germany, which we are not to consider here, is original and important. War is a result of the action of a _herd instinct_, a specific instinct which is peculiar in one respect, in that it acts upon other instincts but has no definite motor reactions of its own. War is the result of the action of the herd instinct in man upon the old instinct of aggression. At least aggressive war is. Men in all their social relations show the play of these instincts; in war it is the old aggressive instinct, the old passion of the pack, that dominates them; and it is the ancestral herd-fears that overcome them in their panics. It is the herd instinct that makes men in groups so highly sensitive to the leader, whose relations to the herd or pack are always dependent upon their recognizing him as one of the group; that is, as acting in accordance with the desires of the herd. It is by the union of the herd, Murray says, or through the herd instinct, that suppressed unconscious impulses are given an opportunity to operate; when the human herd is excited by any external stimulus, the old types of reaction are brought into play. Curiously, in such times, leadership may be assumed by eccentric and even abnormal members of the group--by those who are governed by perverted instincts; by men who are touched with the mania of suspicion, or who even suffer from homicidal mania.