This organism was alive, penetrated throughout by the same essence as the soul which maintains our life and thought. This soul was an igneous breath of which the moral corruption was conceived quite materially. When it gave itself up to the desires of the senses, to corporeal passions, its substance thickened and was troubled, and the mud of this pollution adhered to it like a crust. When the soul left the body at the time of death, it became a spirit like the multitude of demons who peopled the atmosphere. But its lot varied in accordance with its condition. If it were laden with matter, its weight condemned it to float in the densest air, the damp-charged gas which immediately surrounded the earth, and its very composition then caused it to reincarnate itself in new bodies.[82] But if it had remained free from all alloy its lightness caused it to pass immediately through this heavier layer of air and bore it to the higher spaces. It stopped in this ascension when, within the ether which was about the moon, it found itself in surroundings like its own substance. Some elect beings, the divine spirits of the sages, kept such purity that they rose through the ether as far as the highest astral spheres. In this system the doctrine of immortality is seen to be closely knit up with cosmography. If Posidonius has largely borrowed these ideas from the platonising Pythagorism of his period, he forsook this philosophy on an essential point. As a Stoic he did not admit the transcendency of God. For him, God was immanent in the universe; the seat of the directing reason of the world (ἡγεμονικόν) was the sphere of the fixed stars, which embraced all other spheres and determined their revolutions. There too, at the summit of the world but not outside it, the spirits of the blessed gathered; from these high peaks they delighted to observe earthly happenings; and when a pious soul tried to rise to them, these succouring heroes, like our saints, could lend their aid and protection.