There is a side of man's ego which may be called the animal side; and yet it is worse than an animal side, for there are tame animals which have a tendency to love and to respond to love, and which are harmless; but there is a part of man's nature which may be likened to a thorn, or the horn of a rhinoceros, and this ego takes pleasure in hurting others and gets joy from giving pain. From a scientific point of view this is called mania or disease, but psychologically speaking all that is below the human ideal is a defect in man which he could overcome if he knew how.