One aspect of the aggressive habit of man has been too much neglected. It is highly probable that aggression in man has been far more closely related to the emotion of fear than to any assumed predatory instinct. It is a question whether the predatory habit of man, ending in cannibalism and the hunting of animals for food, did not originate in the time of the long battle man must have had with animals in which the animals themselves for the most part played the part of aggressors. It was not for nothing, at any rate, that our animal ancestors took to the trees, and it is certain that the fear element in human nature is very strong and very deeply ingrained. We see throughout animal life fear expressed by aggressive movements, by the show of anger, as well as by flight. This is seen especially clearly in the birds. With all their equipment for the defensive strategy of flight they express fear instinctively by attacking, and this is apparently not a result merely of the habit of defending the young. The great carnivora also attack from fear, and seem normally never to attack such animals as they do not hunt for prey unless they are frightened. The charge of the rhinoceros and other great ungulates is probably always a fear reaction. They appear to have no other aggressive impulses, certainly none connected with the nutritional motives since they are herbivorous in habit. The fear motive is probably much deeper in human nature, both in the lower and the higher social reactions than is commonly supposed, the concealment of fear being precisely a part of the strategy of defense. Fear has created more history than it is usually given credit for. The aggressive motive alone, in all probability, would never have made history such a story of battles as it has been. Nations usually attribute more aggressive intentions and motives to their neighbors than their neighbors possess, and war is certainly often precipitated by an accumulation of mutual distrust and suspicion. Nations are always watching one another for the least signs of aggression on the part of their supposed enemies, an attitude which of course is inspired only by apprehension. Moods of fear and pessimism we say are deeply implanted in the consciousness of man, and we must interpret both his optimism, and all its expressions in philosophy and in religion, and also his aggressive behavior as in large part the result of a conscious or an unconscious effort to overcome his fear. The social consciousness is full of marks of age-long dread and suspicion. Fear of fate, fear of losing identity as a nation, fear of being overrun by an enemy, fear of internal disruption, are strong motives in national life. Fear runs like a dark thread through all the life of nations, and gives to it a quality of mysticism, and a touch of sadness which is so characteristic of much of the deepest patriotism of the world.