The _rationale_ of the evolution of anger is not far to seek. We have seen that fear is the spring of defensive action, and it is obvious that anger is the stimulant to offensive action. Fear is regressive, anger aggressive. Fear is contractile, anger expansive. Fear is the emotion of the pursued, of the prey; anger the emotion of the pursuer, of the predacious. Emotion in the service of life evidently has two great psychic ramifications from this point, and the whole world of emotion-beings, which compose the greater mass of organisms, is hence divided in two great divisions, a fear class and an anger class. Likewise in relation to opposing natural forces as to neighbouring competing and destroying organisms, the same distinction is to be made according as the animal either combats or flees. Shyness or fierceness, timidity or irascibility, these are characters which divide the animate world into two grand antagonistic groups. Zoology has recognised this psychic differentiation as a marked and essential feature in its nomenclature, thus _lepus timidus_. In fact, the most important part of evolution is the psychical; in this, indeed, lies the whole significance and value of the organism. The attainment of more and more advantageous psychic qualities is the main trend of evolution, for psychic power as distinct from main force, like that of the elements, is far and away of the most value in the struggle for existence, and ultimately, as in man, it achieves the subduing all lower powers, natural, vegetable and brute, to its own ends. It is psychical quality, moreover, which determines physical, and not _vice versâ_. Thus it is not the possession of claws, fangs, etc., that makes an animal fierce, but it is fierceness which develops and maintains these weapons of offence. Thus it is, though thus far practically overlooked by scientists, that psychic development, especially on the emotional side, is of the utmost importance as the prime factor and motive in organic processes. The central core of life is emotional capacity, and this in its evolution determines the whole external morphological trend of evolution of organisms which is so closely followed by the science of to-day. But the science of the future is comparative psychology, which, when once placed on a secure basis of interpretation, will determine the real and inner law of evolution as a psychic movement incarnating itself in a succession of animate forms. But a sure method of knowing a psychic fact as such when it occurs, and what, how, and why it is, is yet to be discovered and applied, and extra-human and even extra-ego consciousness is a field, so far, for little else than hypothesis. If this remark be turned against us, we say that our work is mainly a deductive interpretation of the course of psychic evolution from the general standpoint of natural selection, reinforced and illustrated by introspective investigation, and merely