196 OPERATIONS SUBSIDIARY TO INDUCTION. 



sion of the faculties which we actually possess, have heen 

 detected in them. And not only is this always in itself 

 possible, hut it actually happens, in almost all cases in which 

 the obtaining of the right conception is a matter of any con- 

 siderable difficulty. For if there be no new conception 

 required; if one of those already familiar to mankind will 

 serve the purpose, the accident of being the first to whom 

 the right one occurs, may happen to almost anybody ; at 

 least in the case of a set of phenomena which the whole 

 scientific world are engaged in attempting to connect. The 

 honour, in Kepler's case, was that of the accurate, patient, 

 and toilsome calculations by which he compared the results 

 that followed from his different guesses, with the observations 

 of Tycho Brahe ; but the merit was very small of guessing 

 an ellipse ; the only wonder is that men had not guessed 

 it before, nor could they have failed to do so if there had not 

 existed an obstinate a priori prejudice that the heavenly 

 bodies must move, if not in a circle, in some combination of 

 circles. 



The really difficult cases are those in which the conception 

 destined to create light and order out of darkness and confu- 

 sion, has to be sought for among the very phenomena which 

 it afterwards serves to arrange. Why, according to Dr. 

 Whewell himself, did the ancients fail in discovering the laws 

 of mechanics, that is, of equilibrium and of the communica- 

 tion of motion ? Because they had not, or at least had not 

 clearly, the ideas or conceptions of pressure and resistance, 

 momentum, and uniform and accelerating force. And whence 

 could they have obtained these ideas, except from the very 

 facts of equilibrium and motion ? The tardy development of 

 several of the physical sciences, for example of optics, electri- 

 city, magnetism, and the higher generalizations of chemistry, 

 he ascribes to the fact that mankind had not yet possessed 

 themselves of the Idea of Polarity, that is, the idea of oppo- 

 site properties in opposite directions. But what was there to 

 suggest such an idea, until, by a separate examination of 

 several of these different branches of knowledge, it was shown 

 that the facts of each of them did present, in some instances 



