But an end is an effect imagined beforehand and willed, which we cannot bring about immediately but only through a chain of causes. These causes we call the means to the end. They too are willed, but only indirectly and because the end is attainable only through them. These processes to an end are sometimes treated as if the causal succession in them were reversed, so that the last effect appears as the beginning, and the future determines the present; in this sense, the end has been called the end-cause, because the final link of the process causes the beginning. But this is a senseless conception, since the future, that which does not yet exist, cannot now operate. In fact, the succession of causes and effects is no more broken into in the processes leading to an end than in any other processes. When a human being imagines to himself a result and endeavors to bring it about, these mental processes are not future but present; and they are not determined by an influence of the future upon the present, but by an influence of the past upon the present; they follow from experience, that is, from that which has already occurred. They are causal processes in which the activities of understanding and will have part. Hence "ends" exist in nature in so far as they exist in man and the higher animals; but outside these, ends cannot be predicated, unless Nature is regarded either as gifted with imagination and will or as the creation of a being possessing these. But imagination and will require, according to all our experience, a highly developed nervous system, and to assume their existence where such a centralized system does not exist is scientifically injustifiable. Moreover, the laws of thought by no means determine us to inquire after a cause of the whole world, since the concept of cause is applicable only to changes, not, however, to enduring existences and their qualities. Or let us assume that we had discovered an end set by Nature. Then, either it would appear useless to interfere with its attainment and unnecessary to assist in it, or it would appear to us possible to oppose this end. In this latter case, cause must be shown why we should assist, or should resist, the process of Nature. Many philosophers have said that man should live according to his own nature. If the word "nature" here denotes the totality of his characteristics, it is evident that the worst actions are not less natural than the best. Therefore, the word nature cannot, as here used, have this sense; the natural in this sense is not identical with the moral. Nor can the term as here used refer to the usual, for in that case the greatest moral excellence, as unusual, must be rejected. Nor can it be used to designate the more primary, for in that case, again, the later developments of benevolence and truthfulness should be rejected.