300 



INDUCTION. 



In the case last mentioned, this first 

 condition is of easy fulfilment. That 

 social phenomena depend on the acts 

 and mental impressions of human be- 

 ings never could have been a matter 

 of any doubt, however imperfectly it 

 may have been know^n either by what 

 laws those impressions and actions 

 are governed, or to what social con- 

 sequences their laws naturally lead. 

 Neither, again, after physical science 

 had attained a certain development, 

 could there be any real doubt where 

 to look for the laws on which the 

 phenomena of life depend, since they 

 must be the mechanical and chemical 

 laws of the solid and fluid substances 

 composing the organised body and 

 the medium in which it subsists, 

 together with the peculiar vital laws 

 of the different tissues constituting 

 the organic structure. In other cases 

 really far more simple than these, it 

 was much less obvious in what quarter 

 the causes were to be looked for, as 

 in the case of the celestial phenomena. 

 Until, by combining the laws of cer- 

 tain causes, it was fotind that those 

 laws explained all the facts which ex- 

 perience had proved concerning the 

 heavenly motions, and led to predic- 

 tions which it always verified, man- 

 kind never knew that those were the 

 causes. But whether we are able to 

 put the question before or not until 

 after we have become capable of an- 

 swering it, in either case it must be 

 answered ; the laws of the diffei^ent 

 causes must be ascertained before we 

 can proceed to deduce from them the 

 conditions of the effect. 



The mode of ascertaining those laws 

 neither is nor can be any other than 

 the fourfold method of experimental 

 inquiry, already discussed. A few 

 remarks on the application of that 

 method to cases of the Composition 

 of Causes are all that is requisite. 



It is obvious that we cannot expect 

 to find the law of a tendency by an 

 induction from cases in which the 

 tendency is counteracted. The laws 

 of motion could never have been 

 brought to light from the observa- 



tion of bodies kept at rest by the 

 equilibrium of opposing forces. Even 

 where the tendency is not, in the ordi- 

 nary sense of the word, counteracted, 

 but only modified, by having its 

 effects compounded with the effects 

 arising from some other tendency or 

 tendencies, we are still in an un- 

 favourable position for tracing, by 

 means of such cases, the law of the 

 tendency itself. It would have been 

 scarcely possible to discover the law 

 that every body in motion tends to 

 continue moving in a straight line, by 

 an induction from instances in which 

 the motion is deflected into a curve, 

 by being compounded with the effect 

 of an accelerating force. Notwith- 

 standing the resources afforded in this 

 description of cases by the Method 

 of Concomitant Variations, the prin- 

 ciples of a judicious experimentation 

 prescribe that the law of each of the 

 tendencies should be studied, if pos- 

 sible, in cases in which that tendency 

 operates alone, or in combination with 

 no agencies but those of which the 

 effect can, from previous knowledge, 

 be calculated and allowed for. 



Accordingly, in the cases, unfortu- 

 nately very numerous and important, 

 in which the causes do not suffer 

 themselves to be separated and ob- 

 served apart, there is much difficulty 

 in laying down with due certainty 

 the inductive foundation necessary to 

 support the deductive method. This 

 difficulty is most of all conspicuous 

 in the case of physiological pheno- 

 mena : it being seldom possible to 

 separate the different agencies which 

 collectively compose an organised 

 body, without destroying the very phe- 

 nomena which it is our object to in- 

 vestigate : 

 " Following life, in creatures we dissect, 



We lose it in the moment we detect." 



And for this reason I am inclined to 

 the opinion that physiology (greatly 

 and rapidly progressive as it now is) 

 is embarrassed by greater natural 

 difficulties, and is probably suscep- 

 tible of a less degree of ultimate per- 

 fection than even the social sciencCj 



