sense-knowledge and induction alone, to penetrate the mysteries of nature. [Sidenote: Copernicus.] Only one name remains with which that of Bruno is indelibly associated--that of Copernicus, whose _De orbium coelestium Revolutionibus_ was published in 1543. It was his theory of the solar system, coinciding as it seemed with that of the most ancient philosophers, that gave the decisive trend to Bruno's thought, holding him fast to the one all-important fact that the earth is not the centre of the universe but one of its humblest members. Without the solid arguments of Copernicus, Bruno's superb conception of the cosmic system would have remained a dream, an intuition of genius, rather than a well-grounded forecast of modern scientific discovery. "There is more understanding," said Bruno, "in two of his chapters than in the whole philosophy of nature of Aristotle and all the Peripatetics.[245] Grave, thoughtful, careful, and mature in mind, not inferior to any of the astronomers that went before him--in natural judgment far superior to Ptolemy, Hipparch, Eudoxus, and all the others that have walked in their footsteps--a height he attained by freeing himself from the prejudices, not to say blindness, of the vulgar philosophy. Yet he did not get beyond it; being more a student of mathematics than of nature, he was unable wholly to uproot all unfitting, vain principles, to solve all contrary difficulties, liberate both himself and others from so many vain inquiries, and fix their contemplation on things abiding and sure. With all that, who can sufficiently appraise the greatness of this German, who paid little heed to the foolish multitude, and stood solid against the torrent of opposing belief. Although almost destitute of living reasons for weapons, he took up those cast-off and rusty fragments that he could get to his hand from antiquity; repolished them, brought the pieces together, mended them, so that through his arguments--mathematical rather than physical though they were--he made a cause that had been ridiculed, despised, neglected, to be honoured and prized, to seem more probable than its contrary, and certainly more suitable and expeditious for calculation."[246] Copernicus had put forward the theory as a hypothesis merely, and had shown how much more simply the different positions of the sun and planets as seen from the earth could be explained by it, and how much more accurately they could be calculated. In the Epistle prefixed to his work (said by Bruno not to be by Copernicus himself), the reader was warned of the folly of taking this hypothesis as true. To Bruno the contrary of the hypothesis was absurd. Bruno did not appreciate the mathematical proofs of Copernicus, and constantly spoke of him as too much of a mathematician, too little of a physicist: his own mathematical demonstrations were, however, much less successful than those of his predecessor.[247] CHAPTER II THE FOUNDATIONS OF KNOWLEDGE[248]