INDUCTIVE EPOCH OF NEWTON. 189 



the conception of the law, and the moulding this 

 conception in such a form as to correspond with 

 known realities. The idea of mechanical force as 

 the cause of the celestial motions, had, as we have 

 seen, been for some time growing up in men's 

 minds; had gone on becoming more distinct and 

 more general ; and had, in some persons, approached 

 the form in which it was entertained by Newton. 

 Still, in the mere conception of universal gravita- 

 tion, Newton must have gone far beyond his prede- 

 cessors and contemporaries, both in generality and 

 distinctness ; and in the inventiveness and sagacity 

 with which he traced the consequences of this con- 

 ception, he was, as we have shown, without a rival, 

 and almost without a second. As to the facts which 

 he had to include in his law, they had been accu- 

 mulating from the very birth of astronomy; but 

 those which he had more peculiarly to take hold of, 

 were the facts of the planetary motions as given by 

 Kepler, and those of the moon's motions as given 

 by Tycho Brahe and Jeremy Horrox. 



We find here occasion to make a remark which 

 is important in its bearing on the nature of pro- 

 gressive science. What Newton thus used and re- 

 ferred to as facts, were the laws which his prede- 

 cessors had established. What Kepler and Horrox 

 had put forth as "theories," were now established 

 truths, fit to be used in the construction of other 

 theories. It is in this manner that one theory is 

 built upon another ; that we rise from particulars 



