540 INDUCTION. 



tested by that indispensable element of a rational Deductive 

 Method, -verification by specific experience. Between the pri- 

 mitive method of Deduction and that which I have attempted 

 to characterize, there is all the difference which exists between 

 the Aristotelian physics and the Newtonian theory of the 

 heavens. 



It would, however, be a mistake to expect that those great 

 generalizations, from which the subordinate truths of the more 

 backward sciences will probably at some future period be de- 

 duced by reasoning (as the truths of astronomy are deduced 

 from the generalities of the Newtonian theory) , will be found, 

 in all, or even in most cases, among truths now known and 

 admitted. We may rest assured, that many of the most 

 general laws of nature are as yet entirely unthought of ; and 

 that many others, destined hereafter to assume the same cha- 

 racter, are known, if at all, only as laws or properties of some 

 limited class of phenomena ; just as electricity, now recognised 

 as one of the most universal of natural agencies, was once 

 known only as a curious property which certain substances 

 acquired by friction, of first attracting and then repelling light 

 bodies. If the theories of heat, cohesion, crystallization, and 

 chemical action, are destined, as there can be little doubt that 

 they are, to become deductive, the truths which will then be 

 regarded as the principia of those sciences would probably, if 

 now announced, appear quite as novel* as the law of gravita- 

 tion appeared to the cotemporaries of Newton ; possibly even 

 more so, since Newton's law, after all, was but an extension of 

 the law of weight that is, of a generalization familiar from of 

 old, and which already comprehended a not inconsiderable 

 body of natural phenomena. The general laws of a similarly 

 commanding character, which we still look forward to the dis- 

 covery of, may not always find so much of their foundations 

 already laid. 



These general truths will doubtless make their first ap- 

 pearance in the character of hypotheses ; not proved, nor even 



* Written before the rise of the new views respecting the relation of heat 

 to mechanical force ; but confirmed rather than contradicted by them. 



