$ i 5 i] Estimate of Kepler's Work 197 



were too imperfect for him to have made real progress in 

 this direction. 



151. There are few astronomers about whose merits such 

 different opinions have been held as about Kepler. There 

 is, it is true, a general agreement as to the great import- 

 ance of his three laws of planetary motion, and as to the 

 substantial value of the Rudolphine Tables and of various 

 minor discoveries. These results, however, fill but a small 

 part of Kepler's voluminous writings, which are encumbered 

 with masses of wild speculation, of mystic and occult 

 fancies, of astrology, weather prophecies, and the like, which 

 are not only worthless from the standpoint of modern 

 astronomy, but which unlike many erroneous or imperfect 

 speculations in no way pointed towards the direction in 

 which the science was next to make progress, and must 

 have appeared almost as unsound to sober-minded con- 

 temporaries like Galilei as to us. Hence as one reads 

 chapter after chapter without a lucid still less a correct idea, 

 it is impossible to refrain from regrets that the intelligence 

 of Kepler should have been so wasted, and it is difficult 

 not to suspect at times that some of the valuable results 

 which lie imbedded in this great mass of tedious specula- 

 tion were arrived at by a mere accident. On the other 

 hand, it must not be forgotten that such accidents have a 

 habit of happening only to great men, and that if Kepler 

 loved to give reins to his imagination he was equally im- 

 pressed with the necessity of scrupulously comparing 

 speculative results with observed facts, and of surrendering 

 without demur the most beloved of his fancies if it was 

 unable to stand this test, If Kepler had burnt three- 

 quarters of what he printed, we should in all probability 

 have formed a higher opinion of his intellectual grasp and 

 sobriety of judgment, but we should have lost to a great 

 extent the impression of extraordinary enthusiasm and 

 industry, and of almost unequalled intellectual honesty, 

 which we now get from a study of his works. 



