456 OPERATIONS SUBSIDIARY TO INDUCTION. 



mental operation. And inasmuch as such a comparison is a necessary pre- 

 liminary to Induction, it is most true that Induction could not go on with- 

 out general conceptions. 



§ 2. But it does not therefore follow that these general conceptions must 

 have existed in the mind previously to the comparison. It is not a law of 

 our intellect, that in comparing things with each other and taking note 

 of their agreement we merely recognize as realized in the outward world 

 something that we already had in our minds. The conception originally 

 found its way to us as the result of such a comparison. It was obtained 

 (in metaphysical phrase) by abstraction from individual things. These 

 things may be things which we perceived or thought of on former occa- 

 sions, but they may also be the things which we are perceiving or thinking 

 of on the very occasion. When Kepler compared the observed places of 

 the planet Mars, and found that they agreed in being points of an elliptic 

 circumference, he applied a general conception which was already in his 

 mind, having been derived from his former experience. But this is by no 

 means universally the case. When we compare several objects and find 

 them to agree in being white, or when we compare the various species of 

 ruminating animals and find them to agree in being cloven-footed, we have 

 just as much a general 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 con- 

 ceptions with us, and superinduce them (to adopt Dr.Whewell's expres- 

 sion) upon the facts : because in these simple cases every body sees that 

 the very act of comparison which ends in our connecting the facts by 

 means of the conception, may be the source from which we derive the con- 

 ception 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 acquire 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 superinduce it upon the facts ; he could not evolve it 

 out of them : if he had not already had the idea, he Avould not have been 

 able to acquire it by a comparison of the planet's positions. But this in- 

 ability was a mere accident; the idea of an ellipse could have been ac- 

 quired from the paths of the planets as effectually as from any thing else, 

 if the paths had not happened to be invisible. 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 abstracted our original idea of an ellipse from the 

 planetary orbit. Indeed, every conception which can be made the instru- 

 ment for connecting a set of facts, might have been originally evolved from 

 those very facts. The conception is a conception of something; and that 

 which it is a conception of, is really in the facts, and might, under some 

 supposable circumstances, or by some supposable extension 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 almost all cases in 

 which the obtaining of the right conception is a matter of any considera- 

 ble 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 any body ; 

 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, patient, and toilsome calculations by which he com- 



