240 THE PRINCIPLES OF SCIENCE. 



rests in his position is not so far from right as he who, 

 proceeding in a wrong direction, is ever increajiipg his 

 distance/ 



Arago presented a conspicuous example of Jhis high 

 quality of mind, as Faraday remarks ; for whenihe made 

 known his curious discovery of the relation of Mijagnetic 

 needle to a revolving copper plate, a number ojKipposed 

 men of science in different countries gave iB^diate and 

 confident explanations of it, which were all wrong. But 

 Arago, who had both discovered the phenomenon and 

 personally investigated its conditions, declined to put 

 forward publicly any theory at all. 



*At the same time we must not suppose that the truly 

 philosophic mind can tolerate a state of doubt, while a 

 chance of decision remains open. In science nothing like 

 compromise is possible, and truth must be one. Hence, 

 doubt is the confession of ignorance, and must involve 

 a painful feeling of incapacity. But doubt lies between 

 error and truth, so that if we choose wrongly we are 

 further away than ever from our goal. 



Summing up, then, it would seem as if the mind of 

 the great discoverer must combine almost contradictory 

 attributes. He must be fertile in theories and hypotheses, 

 and yet full of facts and precise results of experience. 

 He must entertain the feeblest analogies, and the merest 

 guesses at truth, and yet he must hold them as worthless 

 till they are verified in experiment. When there are any 

 grounds of probability he must hold tenaciously to an 

 old opinion ; and yet he must be prepared at any moment 

 to relinquish it when a single clearly contradictory fact is 

 encountered. 'The philosopher,' says Faraday k , ' should 

 be a man willing to listen to every suggestion, but deter- 

 mined to judge for himself. He should not be biassed by 



k Bence Jones, 'Life of Faraday/ vol. i. p. 225. 



