We find the justification of ancestor worship in the immortality of the reproductive cells, and in the continuity of their series. This should also take a part in the origin of the conception of the soul. Spencer derives the conception of the existence of the soul from dreams, and from the imagination of the mentally afflicted. The savage dreams he is hunting, and wakes up to find himself at home. In his dream he talks with friends who are not present where he sleeps; he may even in the course of his dream encounter the dead. From this he draws the conclusions--(1) that he himself has two persons, one hunting while the other sleeps; (2) that his acquaintances also have a double existence; and, from those cases in which he met with the dead, (3) that they are not only double persons, but that one of the persons is dead while the other continues to live. Thus, according to Spencer, the idea arises that man consists of two separable thinking parts, and that one of these can survive the other. When a person faints and recovers, we say he comes to himself. That is, a part of his person left him and has returned. But in this case, as in the dream, the body has not divided, so that in a swoon the outgoing portion is not corporeal. The savage will think that this is what remains alive after death, for he is incapable of distinguishing between a swoon and death. Then he will associate the part which leaves the body during a swoon with that which gives life, and some will regard the heart, which fails to beat after death, and others the breath, which ceases when life does, as this life-giving part or soul. Thus far I am quoting from Spencer. The conception of the soul, which has thus arisen, has been utilized by astute priests to obtain power over their fellow-men; while the genuine founders of religions have made use of it, and by threats of punishment, and promises of reward, have tried to induce mankind to live uprightly. With this purpose in view, the teachers of religion have changed the original conception of the soul and have added to it the attribute of absolute immortality and eternal duration, an attribute which is in no way connected by people in a low state of development with their conception of the soul. At the present time among the religions of all civilized people the undying soul plays an extraordinarily important part.