Nature, he said, is the same in kind, in its substance, and in its elements, throughout its whole extent--a daring conception for a time when the empyrean and all space beyond it were still regarded as the special abode of divinity. He reminded his opponents of his own childish experiences:--when from Cicala he looked towards Mount Vesuvius, he thought it dark, gloomy, bare of trees and flowers; but when he approached it, he found it fairer than Cicala itself, while now the latter looked bare and dark.[339] The Aristotelians were committing a similar error in judging the distant stars and the firmament to be in reality as they appeared to our eyes, and in denying the existence of that which was not visible to us. "As the philosopher must not believe what cannot be demonstrated by evidence, so neither must he foolishly despise or find fault with what cannot be disproved by reason."[340] Had men, instead of bending so long over the books of Aristotle and his commentators, the _nebulosa volumina_, but turned their eyes to the book and light of nature, they would have formed a far different conception of the constitution of the heavens than that of the eight, nine, ten, or more spheres and innumerable epicycles of the Ptolemaic system. Bruno showed how as we rise from the surface of the earth our horizon becomes wider, while in detail less vivid, and he supposed himself to continue the ascension upwards to the surface of the moon.[341] A few miles away tree and mountain would not be distinguishable from the rest of the earth, but we should perceive only a wide circle of light with dark spots, the appearance of sea and of land respectively. As the distance increased the form of the earth would become more visible while it lost all appearance of opacity, and the whole would seem continuous light. As we neared the moon, the earth would come to appear exactly as the moon does to us from the earth. The moon also revolves round its own axis, and from it, as with us, the universe will appear to revolve round it as centre. It had been said that the appearance of the heavenly bodies had always been and continued to be the same, but Bruno points to the fact that although a mountain, when seen from at hand, changes its face from day to day, and from season to season, yet from a distance it seems always the same.[342] It is owing to the distance that the face of the moon appears to us never to change, although it is certainly subject to as many alterations as the earth itself; and to the dwellers on the moon the earth will appear equally changeless. The light and shadow seen on the surface of the moon are due to the variety of sea and land in it, the one reflecting light, the other absorbing. On the moon, as on the earth, Nature is in continuous change: for example, the relative positions of sea and land are ever altering; but the magnitude of the distance renders these invisible, and more especially the minuteness