If we relied on the divisions of the heavens we find in the exoteric fragments of the Pythagoreans, this astronomy would be similar to that of Ptolemy; the earth motionless and the sun with the planets and the whole of the firmament turning round it. The very principle of this astronomy, however, warns us that it is purely symbolical. In the centre of his universe Pythagoras places Fire (of which the sun is only a reflection). Now in the whole of Eastern esoterism, Fire is the representative sign of Spirit, of divine, universal Consciousness. What our philosophers generally take as the natural philosophy of Pythagoras and Plato is accordingly nothing else than an imaged description of their secret philosophy, clear and light-giving to initiates, but all the more impenetrable by the mass of people as it was considered to be simple natural philosophy. We must consequently seek therein a kind of cosmography of the life of souls and nothing else. The sublunary region designates the sphere in which terrestrial attraction operates and is called the circle of generation. Initiates mean by this that for us the earth is the region of corporeal life. Here take place all the operations accompanying the incarnation and disincarnation of souls. The sphere of the six planets and of the sun responds to ascending categories of spirits. Olympus, conceived as a rolling sphere, is called the heaven of the stationary, because it is assimilated to the sphere of perfect souls. This infantile astronomy accordingly masks a conception of the spiritual universe. Everything, nevertheless, inclines us to believe that the initiates of old, and especially Pythagoras, had far more correct notions of the physical universe. Aristotle positively affirms that the Pythagoreans believed in the movement of the earth around the sun. Copernicus asserts that the idea of the rotation of the earth on its axis came to him whilst reading, in Cicero, that a certain Hycetas of Syracuse had spoken of the daily motion of the earth. Pythagoras taught the double movement of the earth to his disciples of the third degree. Without having the exact measurements of modern science, he knew, as did the priests of Memphis, that the planets which come from the sun turn around it; that the stars are so many solar systems governed by the same laws as ours, and that each has its place in the immense universe. He also knew that each solar world forms a small universe which has its correspondence in the spiritual world and its own heaven. The planets served to mark the scale thereof. Still, these notions which would have overthrown popular mythology, and would have been set down by the people as sacrilegious, were never entrusted to popular writing. They were taught only under the seal of profound secrecy.[16]