ABSTRACTION. 195 



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 &quot; a white thing,&quot; or the con 

 ception of &quot; a cloven-footed animal.&quot; But no one supposes that 

 we necessarily bring these conceptions with us, and superinduce 

 them (to adopt Dr. Whewell s expression) upon the facts : 

 because in these simple cases everybody 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 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 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 would not have been able to acquire it by a comparison 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 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 concep 

 tion 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 something ; and that which 

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

 some supposable circumstances, or by some supposable exten- 



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