Of this physical world, uninteresting in itself, Man is a part. His body, like other matter, is composed of electrons and protons, which, so far as we know, obey the same laws as those not forming part of animals or plants. There are some who maintain that physiology can never be reduced to physics, but their arguments are not very convincing and it seems prudent to suppose that they are mistaken. What we call our “thoughts” seem to depend upon the organization of tracks in the brain in the same sort of way in which journeys depend upon roads and railways. The energy used in thinking seems to have a chemical origin; for instance, a deficiency of iodine will turn a clever man into an idiot. Mental phenomena seem to be bound up with material structure. If this be so, we cannot suppose that a solitary electron or proton can “think”; we might as well expect a solitary individual to play a football match. We also cannot suppose that an individual’s thinking survives bodily death, since that destroys the organization of the brain, and dissipates the energy which utilized the brain-tracks. God and immortality, the central dogmas of the Christian religion, find no support in science. It cannot be said that either doctrine is essential to religion, since neither is found in Buddhism. (With regard to immortality, this statement in an unqualified form might be misleading, but it is correct in the last analysis). But we in the West have come to think of them as the irreducible minimum of theology. No doubt people will continue to entertain these beliefs, because they are pleasant, just as it is pleasant to think ourselves virtuous and our enemies wicked. But for my part I cannot see any ground for either. I do not pretend to be able to prove that there is no God. I equally cannot prove that Satan is a fiction. The Christian God may exist; so may the Gods of Olympus, or of ancient Egypt, or of Babylon. But no one of these hypotheses is more probable than any other: they lie outside the region of even probable knowledge, and therefore there is no reason to consider any of them. I shall not enlarge upon this question, as I have dealt with it elsewhere.[A] [A] See my _Philosophy of Leibniz_, Chapter XV.