454 OPERATIONS SUBSIDIARY TO INDUCTION. 



blance between the phenomenon described and something else ; in pointing 

 out something which the series of observed places of a planet resembles, it 

 points out something in which the several places themselves agree. If the 

 series of places correspond to as many points of an ellipse, the places them- 

 selves agree in being situated in that ellipse. We have, therefore, by the 

 same process which gave us the description, obtained the requisites for an 

 induction by the Method of Agreement. The successive observed places 

 of the earth being considered as effects, and its motion as the cause which 

 produces them, we tind that those effects, that is, those places, agree in the 

 circumstance of being in an ellipse. We conclude that the remaining ef- 

 fects, the places which have not been observed, agree in the same circum- 

 stance, and that the Imc of the motion of the earth is motion in an ellipse. 



The Colligation of Facts, therefore, by means of hypotheses, or, as Dr. 

 Whewell prefers to say, by means of Conceptions, instead of being, as he 

 supposes, Induction itself, takes its proper place among operations subsid- 

 iary to Induction. All Induction supposes that we have previously com- 

 pared the requisite number of individual instances, and ascertained in what 

 circumstances they agree. The Colligation of Facts is no other than this 

 preliminary operation. When Kepler, after vainly endeavoring to connect 

 the observed places of a planet by various hypotheses of circular motion, 

 at last tried the hypotheses of an ellipse and found it answer to the phe- 

 nomena; what he really attempted, first unsuccessfully and at last success- 

 fully, was to discover the circumstance in which all the observed positions 

 of the planet agreed. And when he in like manner connected another set 

 of observed facts, the periodic times of the different planets, by the propo- 

 sition that the squares of the times are proportional to the cubes of the 

 distances, what he did was simply to ascertain the property in which the 

 periodic times of all the different planets agreed. 



Since, therefore, all that is true and to the purpose in Dr. Whewell's 

 doctrine of Conceptions might be fully expressed by the more familiar 

 term Hypothesis; and since his Colligation of Facts by means of appro- 

 priate Conceptions, is but the ordinary process of finding by a comparison 

 of phenomena, in what consists their agreement or resemblance ; I would 

 willingly have confined myself to those better understood expressions, and 

 persevered to the end in the same abstinence which I have hitherto ob- 

 served from ideological discussions; considering the mechanism of our 

 thoughts to be a topic distinct from and irrelevant to the principles and 

 rules by which the trustworthiness of the results of thinking is to be esti- 

 mated. Since, however, a work of such high pretensions, and, it must also 

 be said, of so much real merit, has rested the whole theory of Induction 

 upon such ideological considerations, it seems necessary for others who 

 follow to claim for themselves and their doctrines whatever position may 

 properly belong to them on the same metaphysical ground. And this is 

 the object of the succeeding chapter. 



