ABSTRACTION. 391 



whom the right one occurs, may happen to ahnost anybody ; at least 

 in the case of a set of phenomena which the "whole scientific world 

 are engaged in attempting to connect. The honor, in Kepler's case, 

 was that of the accurate, j)atient, autl toilsome calculations by which 

 he compared the results that followed from his dilferent guesses, with 

 the observations of Tycho Bralie ; but llu; 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 2>riori j^rt^udice that the heavenly bodies must move, if not 

 in a circle, in some combination of circles. 



The really difficult cases arc those in which the conception, that is 

 to create light and order out of darkness and confusion, has to be sought 

 for among the very phenomena which it afterwards serves to arrange. 

 Why, according to Mr. Whewell himself, did the ancients fail in dis- 

 covering the laws of mechanics, that is, of ecjuilibrium and of the com- 

 munication of motion 1 Because they had not, or at least had not 

 clearly, the ideas or conceptions, of pressure and resistance, momen- 

 tum, 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 j)hysical sciences, 

 for example of optics, electricity, magnetism, and the higher generali- 

 zations of chemistry, Mr. Whewell ascribes to the fact that mankind 

 had not yet possessed themselves of the Idea of Polarity, that is, the 

 idea of opposite 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 at least, the curious phe- 

 nomenon of opposite properties in opposite directions ? The thing 

 w-as superficially manifest only in two cases, those of the magnet, and 

 of electrified bodies; and there the conception was encumbered with 

 the circumstance of material poles, or fixed points in the body itself, in 

 which points this opposition of properties seemed to be inherent. The 

 first comparison and abstraction had led only to this conception of poles ; 

 and if anything corresponding to that conception had existed in the 

 phenomena of chemistry or optics, the difficulty which Mr. Whewell 

 justly considers as so great, would have been extremely small. The 

 obscurity arose from the fact, that the polarities in chemistry and optics 

 were distinct species, though of the same genus, with the polarities in 

 electricity and magnetism : and that in order to assimilate the phe- 

 nomena to one another, it was necessary to compare a polarity without 

 poles, such for instance as is exemplified in the polarization of light, 

 and the polarity w'ith poles, which we see in the magnet : and to recog- 

 nize that these polarities, while different in many other respects, agi"ee 

 in the one character which is exj)ressed by the phrase, opposite prop- 

 erties in opposite directions. From the result of such a comparison it 

 was that the minds of scientific men formed this new general concep- 

 tion ; between which, and the first confused ftHsling of an analogy 

 between some of the phenomena of light and those of electiicity and 

 magnetism, there is a long intenal, filled up by the labors and more 

 or less sagacious suggestions of many superior minds. 



The conceptions, then, which we emj)loy for the colligation and 

 methodization of facts, do not develop themselves from within, but are 

 impressed upon the mind from without; tliey arc never obtained other- 



