It is by no means our purpose to seek to throw discredit on any of the great religions of the world. To say that they have been products of evolution is not to invalidate them. Much that is true and solid has arisen through evolution. To say that they lack scientific evidence is not to question their validity. Many of the subjects with which they deal lie beyond the reach of scientific evidence. Science has hitherto dealt strictly with the physical; it has made almost no effort to test the claims of the spiritual. In fact, the highest of these claims, that of the existence of a deity, must lie forever beyond its reach. God may exist, and science grope for Him through eternity in vain. Finite facts can never gauge the infinite. Proofs and disproofs alike have been offered of the existence of an infinite deity, but the problem remains unsolved. None of these proofs or disproofs are positive; they all depend on ideal conceptions, and ideas are always open to question; positive facts on either side of the argument are, and are always likely to be, wanting, and the belief in God must be based on other than scientific grounds. But when we come down to the lower levels of the domain of the spiritual we find ourselves on firmer ground. Here we are dealing with the finite, not with the infinite, and nothing that is finite can lie beyond the boundaries of investigation, however long it may take to reach it. The question of the existence of spirits, for instance,--that much mooted problem of the immortality, or at least of the future existence, of man, which forms so prominent an element in modern religion,--dwells within the possible reach of science, and the attempt to deal with it by scientific evidence may reasonably be made. When we pass beyond the realm of the senses we find ourselves in a kingdom peopled by stupendous forms and forces,--space, time, matter, energy, and perhaps infinite consciousness,--all in their ultimate conditions too vast for the finite mind to grasp, all presenting problems open to speculation, but beyond the reach of demonstration. But below these lie finite possibilities which the human mind may now be, or may become, capable of comprehending, and prominent among these lies the problem just mentioned, that of the existence of a spiritual substratum in man, a soul which is capable of surviving the death of the body. This is a subject with which all of us are deeply and intimately concerned, and it may be well to close this volume with a brief glance at its status as a scientific question.