mode of action of the first three and that of the last. The first three, which we may, for convenience and without prejudice, call the primitive instincts, have in common the characteristic of attaining their maximal activities only over short periods and in special sets of circumstances, and of being fundamentally pleasant to yield to. They do not remain in action concurrently, but when the circumstances are appropriate for the yielding to one, the others automatically fall into the background, and the governing impulse is absolute master. Thus these instincts cannot be supposed at all frequently to conflict amongst themselves, and the animal possessing them alone, however highly developed his consciousness might be, would lead a life emotionally quite simple, for at any given moment he would necessarily be doing what he most wanted to do. We may, therefore, imagine him to be endowed with the feelings of free-will and reality to a superb degree, wholly unperplexed by doubt and wholly secure in his unity of purpose. {48}
The appearance of the fourth instinct, however, introduces a profound change, for this instinct has the characteristic that it exercises a controlling power upon the individual from without. In the case of the solitary animal yielding to instinct the act itself is pleasant, and the whole creature, as it were body and soul, pours itself out in one smooth concurrence of reaction. With the social animal controlled by herd instinct it is not the actual deed which is instinctively done, but the order to do it which is instinctively obeyed. The deed, being ordained from without, may actually be unpleasant, and so be resisted from the individual side and yet be forced instinctively into execution. The instinctive act seems to have been too much associated in current thought with the idea of yielding to an impulse irresistibly pleasant to the body, yet it is very obvious that herd instinct at once introduces a mechanism by which the sanctions of instinct are conferred upon acts by no means necessarily acceptable to the body or mind. This, of course, involves an enormous increase of the range through which instinct can be made use of. Its appearance marks the beginning of the multifarious