Consequently, it is in a very deep sense that the initiate poets of old called sleep _the brother of death_. A veil of forgetfulness separates the sleeping from the waking state, like birth and death, and, just as our earthly life is divided into two parts always alternating, so also the soul, in the immensity of its cosmic evolution, alternates between incarnation and spiritual life, between earth and heaven. This alternate passage from one plane of the universe to another, this reversing of the poles of its being, is no less necessary for the development of the soul than alternate waking and sleeping is necessary for the bodily life of man. When passing from one existence to the other, we need the waters of Lethe. In this present existence, a salutary veil conceals from us past and future alike. But oblivion is not complete, since light passes through the veil. Innate ideas alone prove a former existence. There is more, however; we are born with a world of vague remembrances, mysterious impulses, divine presentiments. In children born of gentle quiet parents we find outbursts of wild passions which atavism does not sufficiently explain, and which come from a former existence. Sometimes in the humblest life we find fidelity to a sentiment or an idea, altogether sublime and inexplicable. Is not this a result of the promises and oaths of the celestial life? The occult memory the soul has kept of them is stronger than all earthly reasoning. According as it attaches itself to this memory or abandons it, is it seen to overcome or to succumb. True faith consists in this mute fidelity of the soul to itself. For this reason, one may conceive that Pythagoras like all theosophists considered bodily life as a necessary elaboration of the will, and heavenly life as a spiritual growth, an accomplishment.