11. A place is always in harmony with the nature of the beings who must live there. Fish are in water; winged beings are in the air; spiritual beings are in the spiritual or ethereal fluid, even upon the Earth. The ethereal fluid is for the needs of the spirit, as the atmosphere is for the necessities of the body. Now, as fishes cannot live in the air, and terrestrial animals cannot live in an atmosphere too rarefied for their lungs, inferior spirits cannot support the splendor and impression of the most ethereal fluids. They would not die, because spirit cannot die; but an instinctive force keeps them at a distance, as one keeps away from a fire which is too hot, or from a light which is too strong. This is the reason why they cannot go away from the midst appropriate to their nature. In order to change it, it is necessary first to change their nature, that they be despoiled of the material instincts which retain them in material midst. As they become purified and morally transformed, they gradually become identified with purer surroundings, which become a necessity to them, like the eyes of him who has remained a long time in darkness are habituated imperceptibly to the light of day and the splendor of the sun.