The great master of rationalist phenomenalism, David Hume, begins his essay "On the Immortality of the Soul" with these decisive words: "It appears difficult by the mere light of reason to prove the immortality of the soul. The arguments in favour of it are commonly derived from metaphysical, moral, or physical considerations. But it is really the Gospel, and only the Gospel, that has brought to light life and immortality." Which is equivalent to denying the rationality of the belief that the soul of each one of us is immortal. Kant, whose criticism found its point of departure in Hume, attempted to establish the rationality of this longing for immortality and the belief that it imports; and this is the real origin, the inward origin, of his _Critique of Practical Reason_, and of his categorical imperative and of his God. But in spite of all this, the sceptical affirmation of Hume holds good. There is no way of proving the immortality of the soul rationally. There are, on the other hand, ways of proving rationally its mortality. It would be not merely superfluous but ridiculous to enlarge here upon the extent to which the individual human consciousness is dependent upon the physical organism, pointing out how it comes to birth by slow degrees according as the brain receives impressions from the outside world, how it is temporarily suspended during sleep, swoons, and other accidents, and how everything leads us to the rational conjecture that death carries with it the loss of consciousness. And just as before our birth we were not, nor have we any personal pre-natal memory, so after our death we shall cease to be. This is the rational position. The designation "soul" is merely a term used to denote the individual consciousness in its integrity and continuity; and that this soul undergoes change, that in like manner as it is integrated so it is disintegrated, is a thing very evident. For Aristotle it was the substantial form of the body--the entelechy, but not a substance. And more than one modern has called it an epiphenomenon--an absurd term. The appellation phenomenon suffices. Rationalism--and by rationalism I mean the doctrine that abides solely by reason, by objective truth--is necessarily materialist. And let not idealists be scandalized thereby. The truth is--it is necessary to be perfectly explicit in this matter--that what we call materialism means for us nothing else but the doctrine which denies the immortality of the individual soul, the persistence of personal consciousness after death.