4.26 



Ol?ERA'riONS SUBSIDTARY TO II^DUCtlON. 



and find them to agree in being cloven- 

 footed, we have just as much a gene- 

 ral conception in our minds as Kepler 

 had in his ; we have the conception 

 of a "white thing," or the conception 

 of a "cloven-footed animal" But 

 no one supposes that we necessarily 

 bring these conceptions with us, and 

 superinduce them (to adopt Dr. Whe- 

 well's expression) upon the facts ; be- 

 cause in these simple cases every- 

 body sees that the very act of com- 

 parison which ends in our connecting 

 the facts by means of the conception 

 may be the source from which we 

 derive the conception itself. If we 

 had never seen any white object or 

 had neVer seen any cloven-footed 

 animal before, we should at the same 

 time and by the same mental act ac- 

 quire the idea and employ it for the 

 colligation of the observed phenomena. 

 Kepler, on the contrary, really had to 

 bring the idea with him and superin- 

 duce it upon the facts ; he could not 

 evolve it out of them : if he had not 

 already had the idea he would not 

 have been able to acquire it by a com- 

 parison of the planet's positions. But 

 this inability was a mere accident ; 

 the idea of an ellipse could have been 

 acquired from the paths of the planets 

 as effectually as from anything else, if 

 the paths had not happened to be in- 

 visible. If the planet had left a 

 visible track, and we had been so 

 placed that we could see it at the 

 proper angle, we might have ab- 

 stracted our original idea of an ellipse 

 from the planetary orbit. Indeed, 

 every conception which can be made 

 the instrument for connecting a set 

 of facts might have been originally 

 evolved from those very facts. The 

 conception is a conception of some- 

 thing ; and that which it is a concep- 

 tion of is really in the facts, and 

 might, under some supposable circum- 

 stances, or by some supposable exten- 

 sion of the faculties which we actually 

 possess, have been detected in them. 

 And not only is this always in itself 

 possible, but it actually happens in 

 uluiost all cases in which the obtainin"^ 



of the right conception is a matter of 

 any considerable 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 ac- 

 curate, patient, and toilsome calcula- 

 tions by which he compared the re- 

 sults that followed from his diffe- 

 rent 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 d 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 confusion 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 equi- 

 librium and motion ? The tardy de- 

 velopment of several of the physical 

 sciences, for example, of optics, elec- 

 tricity, magnetism, and the higher 

 generalisations of chemistry, he as- 

 cribes to the fact that mankind had 

 not yet possessed themselves of the 

 Idea of Polarity, that is, the idea of 

 opposite properties in opposite direc- ^ 

 tions. But what was there to suggest 

 such an idea, until, by a separate ex- 

 amination of several of these diffe- 





