INDUCTIONS IMPROPERLY SO CALLED. 337 



rence of opinion consists, as well as, in some measure, to 

 account for it. 



Nearly all the definitions of induction, by writers of autho- 

 rity, make it consist in drawing inferences from known cases 

 to unknown ; affirming of a class, a predicate which has been 

 found true of some cases belonging to the class ; concluding, 

 because some things have a certain property, that other things 

 which resemble them have the same property or because a 

 thing has manifested a property at a certain time, that it has 

 and will have that property at other times. 



It will scarcely be contended that Kepler's operation was 

 an Induction in this sense of the term. The statement, that 

 Mars moves in an elliptical orbit, was no generalization from 

 individual cases to a class of cases. Neither was it an exten- 

 sion to all time, of what had been found true at some par- 

 ticular time. The whole amount of generalization which the 

 case admitted of, was already completed, or might have been 

 so. Long before the elliptic theory was thought of, it had 

 been ascertained that the planets returned periodically to the 

 same apparent places; the series of these places was, or might 

 have been, completely determined, and the apparent course of 

 each planet marked out on the celestial globe in an uninter- 

 rupted line. Kepler did not extend an observed truth to 

 other cases than those in which it had been observed : he did 

 not widen the subject of the proposition which expressed the 

 observed facts. The alteration he made was in the predicate. 

 Instead of saying, the successive places of Mars are so and so, 

 he summed them up in the statement, that the successive 

 places of Mars are points in an ellipse. It is true, this state- 

 ment, as Dr. Whewell says, was not the sum of the observa- 

 tions merely ; it was the sum of the observations seen under a 

 new point of view* But it was not the sum of more than the 

 observations, as a real induction is. It took in no cases but 

 those which had been actually observed, or which could have 

 been inferred from the observations before the new point of 

 view presented itself. There was not that transition from 



* Phil. ofDiscov. p. 256. 

 VOL. I. 2,2 



