86 THE HISTORY OF BIOLOGY 



Otherwise Copernicus retained that system practically unaltered; he thus 

 made the sun the immovable centre of the universe, the planets moving in 

 circles round it and the w^hole surrounded by the sphere of fixed stars, such 

 as the ancients imagined it. In reality, then, his theory was less subver- 

 sive than Cusanus's and, as a matter of fact, not without precedents in an- 

 tiquity; but still it attracted far more attention, because it was entirely at 

 variance with what everyone was accustomed to see happening daily before 

 his very eyes. Copernicus spent decades working out his theory, and not 

 until the year before his death did he dare to publish a book on it. It aroused 

 fierce opposition, particularly on religious grounds; the reformers as well as 

 the Jesuits condemned its teachings, while its scientific influence was at first 

 but small, all the more so as the proofs he offered of the truth of his new 

 theory were really rather weak. Shortly after his death, however, a thinker 

 was born who was able to reconcile Copernicus's ideas with those of Cusanus 

 and thereby founded a theory of the universe which in its essentials still holds 

 good today. 



Giordano Bruno wa^born at Nola in south Italy in 1548. As a young 

 man he entered a monastery, but he was far from contented with the life 

 there, was soon suspected of heresy, and saved himself by flight. After this 

 he never found a permanent retreat; excommunicated and persecuted within 

 the Catholic world, he nevertheless found no consolation in the Protestant 

 countries which he visited. Upon returning to Italy he became a victim of 

 the Inquisition and after many years' imprisonment was condemned as a 

 heretic and burnt at the stake in 1600. 



In numerous lectures, disputations, and published works he preached 

 in the countries he visited the new doctrine which cost him his life. In this 

 he takes as a starting-point Cusanus's speculations on infinity, Lucretius' 

 atomic theory, and Copernicus's solar system. On the ideas which he found 

 in these various conceptions he built still further with an originality which 

 ranks him amongst the greatest thinkers of all time, in spite of the fantasy 

 and mysticism with which he, like the other philosophers of the Renaissance, 

 burdens his speculations. In agreement with Cusanus, but still more emphati- 

 cally, Bruno maintains the subjectivity of mental observation; when a man 

 moves, the horizon goes with him, from which we must conclude that there 

 exists no absolute universal centre. On the contrary, both reason and faith 

 demand an infinite world, infinite as God Himself. And, like mental impres- 

 sions, place, movement, and time are relative and dependent upon the po- 

 sition in space from which they are observed. — Nor can the assertion main- 

 tained by Aristotle as to absolutely heavy and absolutely light bodies be 

 true; this being so, there is no meaning whatever in the old belief that planets 

 and fixed stars are lodged in spheres round the earth; on the contrary, they 

 move in their orbits in space freely and by internal force. And like his cosmic 



