TERRESTRIAL ELEMENTS, HOWEVER, DO NOT DEGRADE THE HEAVEN.
It is unlikely that the universal Organism is composed of universal elements. That terrestrial animals are thus composed is certain; but to introduce the terrestrial element into the composition of the heaven would be to admit something contrary to nature, and to the order thereby established. (Epicurus's opinion that) the stars carry terrestrial bodies along in their rapid flight is undemonstrable. Besides, the presence of the earth would be an obstacle to the shine and splendor of the celestial fire.
PLATO POSTULATED THE EXISTENCE OF EARTH AS BASIS OF LIFE.
7. Plato's view[217] is to be accepted. The universe must contain something solid, impenetrable, so that the earth, when established in the middle of the universe, might offer a firm foundation for all the animals that walk on it, and that these animals might possess a certain solidity by the very fact of their terrestriality; so that the earth might, by itself, possess the property of continuousness; that it might be illuminated by fire, might also participate in water, so as not to be desiccated, and so that its parts might unite, and that the air might somewhat lighten its mass.
ELEMENTS ARE KINDRED THROUGH THEIR COMMON GROUND, THE UNIVERSE-BODY.
The earth was mingled with the upper fire not to produce the stars, but because fire has something terrestrial, as earth has something igneous, as a result of all the bodies being contained within the body of the universe. In short, every one of the elements includes mixture of itself and of the other with which it participates. This results from the interrelating community existing within the universe (the "sympathy"). So each element, without combining with any other, borrows some of its properties. For example, water participates in the fluidity of the air, without however mingling therewith; so the earth does not possess the fire, but derives its brightness from it. On the other hand, a mixture would render all properties common to both elements, confounding them together,[218] and would not limit itself to merely approximating earth and fire, that is, a certain solidity with a certain density. On this subject we can invoke the authority of (Plato[219]), "The divinity lit this light in the second circle above the earth," thereby referring to the sun, which he elsewhere calls "the most brilliant star."
By these words he hinders us from admitting that the sun is anything else than fire. He also indicates that fire has no quality other than light, which he considers as distinct from flame, and as possessing only a gentle heat. This light is a body. From it emanates another being that we, by verbal similarity, also call light, and which we acknowledge to be incorporeal. This second kind of light derives from the former, being its flower and brightness, and constitutes the essentially white (that is, brilliant) body (of lightning, or comets). (Unfortunately, however), the word "terrestrial" (which designates the element allied to the fire, as we have said above), we are wont to regard unfavorably because Plato makes the earth consist of solidity, while we speak of the earth as a unity, though (Plato) distinguishes several qualities within this element.
NATURE OF THE CELESTIAL FIRE AND LIGHT.
The fire of which we speak above emits the purest light, and resides in the highest region, by virtue of its nature. These celestial flames are entirely distinct from the earthly flame, which after ascending to a certain height, and meeting a greater quantity of air, becomes extinguished. After ascending, it falls back on to the earth, because (as a comet) it cannot rise any further; it stops in the sublunar regions, though rendering the ambient air lighter. In those cases in which it continues to subsist in higher regions, it becomes weaker, gentler, and acquires a heatless glow, which is but a reflection of the celestial light. The latter, on the other hand, is divided partly among the stars in which it reveals great contrasts of magnitude and color, and partly in the atmosphere. Its invisibility to our eyes is caused both by its tenuity, and transparence, which causes it to become as tangible as pure air, and also because of its distance from the earth.