222 THE PRINCIPLES OF SCIENCE. 



record may remain of more than the hundredth part. 

 There is nothing intrinsically absurd except that which 

 proves contrary to logic and experience. The truest 

 theories involve suppositions which are most inconceiv- 

 able, and no limit can really be placed to the freedom of 

 framing hypotheses. Kepler is an extraordinary instance 

 to this effect. No minor laws of nature are more firmly 

 established than those which he detected concerning the 

 orbits and motions of planetary masses, and on these 

 empirical laws the theory of gravitation was founded. 

 Did we not know by his own writings the multitude of 

 errors into which he fell, we might have imagined that 

 he had some special faculty of seizing on the truth. But, 

 as is well known, he was full of chimerical notions ; his 

 most favourite and long entertained theory was founded 

 on a fanciful analogy between the planetary orbits and 

 the regular solids. His celebrated laws were the outcome 

 of a lifetime of speculation, for the most part vain and 

 groundless. We know this with certainty, because he 

 had a curious pleasure in dwelling upon erroneous and 

 futile trains of reasoning, which most other persons care- 

 fully consign to oblivion. But Kepler's name was des- 

 tined to immortality, on account of the patience with 

 which he submitted his hypotheses to comparison with 

 observation, the candour with which he acknowledged 

 failure after failure, and the perseverance and ingenuity 

 with which he renewed his attack upon the riddles of 

 nature. 



Next after Kepler perhaps Faraday is the physical 

 philosopher who has afforded us the most important mate- 

 rials for gaining an insight into the progress of discovery, 

 by recording erroneous as well as successful speculations. 

 The recorded notions, indeed, are probably at the most a 

 tithe of the fancies which arose in his active brain. As 

 Faraday himself said '.The world little knows how 



