90 THE HISTORY OF BIOLOGY 



Jupiter, the sun-spots, the phases of Venus and Mercury. But it was impossi- 

 ble to reconcile all these new facts with the ancient Aristotelean-Ptolemaic 

 cosmic theory and so Galileo early associated himself with the conception 

 of the universe as enunciated by Copernicus and Bruno. His great fame pro- 

 cured for him the personally brilliant appointment of Astronomer Royal to 

 the Medicean Grand Duke at Florence, with a high salary and no official 

 duties. But in leaving the service of the powerful Venetian Republic he came 

 under the influence of the power of the Roman Church, a circumstance all 

 the more dangerous to him as his new discoveries excited the bitter hostility 

 of the very parties which had condemned Bruno; moreover, he was himself a 

 violent controversialist, who never spared his enemies. His end is a matter 

 of common knowledge — how he was arraigned before the Inquisition on 

 account of a "dialogue" on the solar system and under threat of death was 

 compelled to make a public recantation of his "Copernican error," after 

 which he lived in strict seclusion until his death, in 1641. 



Galileo' s theory 

 Galileo's fundamental importance as a natural philosopher is not based 

 merely upon his discoveries, epoch-making as they are; he has contributed 

 in a still higher degree towards scientific progress through the principles 

 which he laid down and which have become the basis of modern natural 

 philosophy. As we know, Aristotle based his cosmic theory upon the con- 

 trast between form and matter, where form is assumed to be a realization of 

 matter's powers of development; the higher the degree of its realization, the 

 more perfect the form. Therefore the heavenly bodies, with their regular 

 motions, are more form-perfect than the earth, with its many irregularities, 

 while beyond the heavenly spheres is the world of pure form, God, the origin 

 of all forms, the cause of all that happens in the universe. Galileo at once 

 came into conflict with this system through his astronomical discoveries; 

 according to Aristotle, the firmament, as existing nearest to the immutable 

 divine intelligence, was itself immutably regular in its motions. Galileo 

 discovered a great many irregularities; the sun-spots, Jupiter's moons, and all 

 else that the newly-invented telescope brought into the light of day proved 

 the firmament was not such a place of perfection and regularity as had been 

 supposed. On the other hand, the phenomena of motion in bodies here upon 

 earth showed an obedience to law of which the ancients had no notion. 

 Galileo experimented with the free f^ll of bodies, with pendulous motions, 

 and with the motions of bodies along an inclined plane, and discovered in all 

 these phenomena ratios between weights, lengths of time, and rapidity of 

 motion so mathematically regular that he could express them in the form of 

 theorems as capable of demonstration as the old geometrical propositions 

 formulated by Euclid. But it was just through this combination of natural- 

 scientific experiment and mathematical calculation that, as he himself says, 



