Another reason is that it was necessary to be more widely informed than the Chaldæans, in order to be able to contradict the apparent testimony of the senses in regard to the celestial appearances; that it required not only the most refined experimental observation, but the most profound mathematical science; as also the indispensable aid of telescopes, without which it is impossible to discover the phases of Venus, which prove her course around the sun, or to discover the spots in the sun, which demonstrate his motion round his own almost immovable axis. Another reason, not less strong, is that of all those who have attributed this discovery to Pythagoras, no one can positively say how he treated it. Diogenes Laertius, who lived about nine hundred years after Pythagoras, teaches us, that according to this grand philosopher, the number one was the first principle, and that from two sprang all numbers; that body has four elements--fire, water, air, and earth; that light and darkness, cold and heat, wet and dry, are equally distributed; that we must not eat beans; that the soul is divided into three parts; that Pythagoras had formerly been Atalides, then Euphorbus, afterwards Hermotimus; and, finally, that this great man studied magic very profoundly. Diogenes says not a word concerning the true system of the world, attributed to this Pythagoras; and it must be confessed that it is by no means to an aversion to beans that we owe the calculations which at present demonstrate the motion of the earth and planets generally. The famous Arian Eusebius, bishop of Cæsarea, in his "Evangelical Preparation," expresses himself thus: "All the philosophers declare that the earth is in a state of repose; but Philolaus, the peripatetic, thinks that it moves round fire in an oblique circle, like the sun and the moon." This gibberish has nothing in common with the sublime truths taught by Copernicus, Galileo, Kepler, and above all by Newton. As to the pretended Aristarchus of Samos, who, it is asserted, developed the discoveries of the Chaldæans in regard to the motion of the earth and other planets, he is so obscure, that Wallace has been obliged to play the commentator from one end of him to the other, in order to render him intelligible.