Up to the present, the doctrine of immortality has been an essential part of Christianity. The creeds which have come down to us proclaim the faith that Christ Jesus will appear again to judge the quick and the dead. To the average man, religion is absolutely committed to such a belief. It has gone hand in hand with the idea of retribution and reward until the two have grown together. It is not strange, then, that the suspicion that immortality is not justified by physiological and psychological facts is felt to have a grave bearing upon religion. To the vast majority, religion without immortality is like _Hamlet_ with Hamlet left out. Remove the faith in a special providence, likewise, and the edifice around which many religious emotions and values have entwined themselves is no more than a ruin. But the idea of a soul always accompanies the belief {143} in immortality. The experiences which led to the one notion naturally encouraged the other. If the soul can leave the body, it is obviously independent, in large measure, of the latter's fate. Let us glance at some of the experiences whose false interpretation is at the foundation of a belief in an immortal soul inhabiting the body for a little space. It is surprising what an influence was exercised by dreams. We have so completely outgrown this uncritical attitude toward them that it takes some effort to realize how natural it was. For the educated man of to-day, dreams are subjective experiences, that is, experiences which do not contain information about what is happening in the external world. In the jargon of psychology, they are centrally aroused ideas playing about some organic stimulus or some repressed wish. But the savage knew nothing about such distinctions. The dead appeared to the living and talked with them. Patroclus stands before Achilles and chides him. Do not the dead, then, have some sort of life? Many psychological motives combined to convince primitive man of at least a shadowy existence after death. But there was another side to the dream-life. The living went on long journeys, doing strange things, while their bodies rested in the tent. Added to these suggestions, so naturally lending themselves to a spiritistic interpretation, were still others. Certain kinds of sickness are explained by means of the idea of possession. Invisible agents are at work in the world. What can a trance be if not the temporary absence of just such an agent? "Among the Kayans of Borneo, for example, it is the custom for an elderly person learned in such matters to sit beside the corpse, where the soul is {144} supposed to hover for some days after death, and to impart to the latter minute directions for its journey to the land of the dead." We are in the presence, here, of natural illusions, of hypotheses which inevitably arose. Man's first guesses were mistakes. The whole history of science drives this fact home.