A HISTORY OF SCIENCE 



that I have dared to bring the results of my night la- 

 bors to the light of day, after having taken so much care 

 in elaborating them, but is waiting instead to hear how 

 it entered my mind to imagine that the earth moved, 

 contrary to the accepted opinion of mathematicians- 

 nay, almost contrary to ordinary human understand- 

 ing. Therefore I will not conceal from your holiness 

 that what moved me to consider another way of reck- 

 oning the motions of the heavenly bodies was nothing 

 else than the fact that the mathematicians do not 

 agree with one another in their investigations. In 

 the first place, they are so uncertain about the motions 

 of the sun and moon that they cannot find out the 

 length of a full year. In the second place, they apply 

 neither the same laws of cause and effect, in determin- 

 ing the motions of the sun and moon and of the five 

 planets, nor the same proofs. Some employ only con- 

 centric circles, others use eccentric and epicyclic ones,, 

 with which, however, they do not fully attain the de- 

 sired end. They could not even discover nor compute 

 the main thing namely, the form of the universe and 

 the symmetry of its parts. It was with them as if 

 some should, from different places, take hands, feet, 

 head, and other parts of the body, which, although very 

 beautiful, were not drawn in their proper relations, 

 and, without making them in any way correspond, 

 should construct a monster instead of a human being. 

 " Accordingly, when I had long reflected on this un- 

 certainty of mathematical tradition, I took the trouble 

 to read again the books of all the philosophers I could 

 get hold of, to see if some one of them had not once 

 believed that there were other motions of the heavenly 



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