In the true spirit of the Renaissance, however, he appealed to the authority of the ancients, of Aeschylus and Hipparchus of Chios, who, according to Aristotle, regarded the comets as planets.[365] The comets of the sixteenth century,[366] so far as observed, went wholly against the received view that their orbits must lie within the sphere of the moon, and proved that the substance of bodies beyond that sphere was the same as the elementary substance of the earth, as well as that there was penetrable space beyond. Both of these to Bruno were important consequences. Still greater, however, was their importance for humanity, in removing the grounds of the terror which comets and other heavenly wonders had hitherto inspired. "There are some," said Bruno, "who rest their faith in a virtue above and beyond nature, saying that God, who is above nature, creates these appearances in the heavens in order to signify something to us: as if those were not better, nay the very best, signs of divinity which arise in the ordinary course of nature; among which are those of which we speak, for they also are not apart from this order, although their order is hidden from us." To account for the many appearances which seemed to conflict with his new view of the universe, Bruno had recourse to several slight experiments and analogies of daily observation such as a schoolmaster might employ at the present day before his class,[367] but by which even a man of Kepler's intelligence refused then to be convinced; at least he would not openly profess his conviction. Among other fruitful suggestions which Bruno makes is that the sun may perhaps turn on its own axis, and again that it may contain vapour and earth.[368] He had a curious theory that the heat of the sun is only directed outward _from the surface_, not inwards; that this is the general course of radiation; and that it leaves an inner surface of the sun cold, on which solar animals live; finally that meteors are "animals" expelled from the sun! So always the fruitful idea is accompanied by the absurd.