124 STATESMEN AND SAGES and the stars revolved around the world which we inhabit. Not that the Py- thagorean hypothesis was totally forgotten. There were those who believed that the sun, not the earth, is the centre of the great circle in which the heavenly "bodies perform their evolutions ; but the Ptolemaic hypothesis had the ascen- dency beyond all doubt ; and with this hypothesis Copernicus could not rest sat- isfied. It appeared to him beset with insuperable difficulties. True enough, the rotation of the heavens around the earth seemed to be what the human eye be- held, as anyone watched sunrise and sunset. But what the senses thus presented, reason, in its ponderings, was led to contradict. For the notion of a huge mech- anism like the celestial sphere, spinning round the terraqueous globe as its pivot looked unreasonable. To explain it in any way on mathematical principles needed a most complicated array of cycles and epicycles. Symmetry and sim- plicity were wanting in the theory. A priori objections started up against it If the senses pointed to the earth as a centre, reason pointed to a centre else- where Copernicus studied the works of ancient philosophers on the question. He examined mathematical traditions and criticised the opinions of learned pro- fessors. He found accounts of those who had asserted the motion of the earth. " Though," he says, " it appeared an absurd opinion, yet, since I knew that in former times liberty had been permitted to others to figure as they pleased cer- tain circles for the purpose of demonstrating the phenomena of the stars, I con- sidered that to me also it might be easily allowed to try whether, by a supposition of the earth's motion, a better explanation might be found of the revolution of the celestial orbs. Having assumed," he goes on to say, " the motions of the earth, by laborious and long observation I at length found that if the motions of the other planets be compared with the revolution of the earth, not only these phenomena follow from the suppositions, but also that the several orbs and the whole system are so connected in order and magnitude, that no one part can be transposed without disturbing the rest and introducing confusion into the whole universe." What Copernicus was in search of was some simple and symmetrical theory of the appearances of the heavens which would relieve him of the com- plexity and confusion attendant on the Ptolemaic system so popular in the schools. He started from an a priori point of reasoning the only one thought of in his day but he came to certain conclusions which a posteriori examination .n after times abundantly confirmed. He believed that the earth is spherical ; that the earth and the sea constitute a wonderful globe ; that the motions of the heavenly bodies are circular and uni- form, or compounded of circular and uniform motions ; that the earth revolves on its own axis,' and also performs a journey along its own orbit round the sun ; that the sphere of the fixed stars is immensely distant, and that it is impossible to explain the motion of the planets upon the supposition of the earth being their centre. And he distinctly remarks : " It does not shame us to confess that the whole space in which the moon revolves, together with the earth, moves along a great orbit among the planets, round the sun every year ; that the sun remains permanent and immovable, whatever may be its apparent motion." It must be
