OBSERVATION AND EXPERIMENT. 275 



fore, it might antecedently iiave been supposed could stand least in need of 

 artilicial means of production to enable it to be studied ; while the fact is 

 so much the contrary, that without the electric machine, the Leyden jar, 

 and the voltaic battery, we probably should never have suspected the ex- 

 istence of electricity as one of the great agents in nature ; the few electric 

 phenomena we should have known of would have continued to be regard- 

 ed either as supernatural, or as a sort of anomalies and eccentricities in the 

 order of the universe. 



When we have succeeded in insulating the phenomenon which is the 

 subject of inquiry, by placing it among known circumstances, we may pro- 

 duce further variations of circumstances to any extent, and of such kinds 

 as we think best calculated to bring the laws of the phenomenon into a 

 clear light. By introducing one well-defined circumstance after another 

 into the experiment, we obtain assurance of the manner in which the phe- 

 nomenon behaves under an indefinite variety of possible circumstances. 

 Thus, chemists, after having obtained some newly-discovered substance in 

 a pure state (that is, having made sure that there is nothing present which 

 can interfere with and modify its agency), introduce various other sub- 

 stances, one by one, to ascertain whether it will combine with them, or de- 

 compose them, and with what result ; and also apply heat, or electricity, or 

 pressure, to discover what will happen to the substance under each of these 

 circumstances. 



But if, on the other hand, it is out of our power to produce the phenom- 

 enon, and we have to seek for instances in which nature produces it, the 

 task before us is very different. 



Instead of being able to choose what the concomitant circumstances 

 shall be, we now have to discover what they are ; which, when we go be- 

 yond the simplest and most accessible cases, it is next to impossible to do 

 with any precision and completeness. Let us take, as an- exemplification of 

 a phenomenon which we have no means of fabricating artificially, a human 

 mind. Nature produces many ; but the consequence of our not being able 

 to produce them by art is, that in every instance in which we see a human 

 mind developing itself, or acting upon other things, we see it surrounded 

 and obscured by an indefinite multitude of unascertainable circumstances, 

 rendering the use of the common experimental methods almost delusive. 

 We may conceive to what extent this is true, if we consider, among 

 other things, that whenever Nature produces a human mind, she produces, 

 in close connection with it, a body ; that is, a vast complication of physical 

 facts, in no two cases perhaps exactly similar, and most of which (except 

 the mere structure, which we can examine in a sort of coarse way after it 

 has ceased to act), are radically out of the reach of our means of explora- 

 tion. If, instead of a human mind, we suppose the subject of investiga- 

 tion to be a human society or State, all the same diflUculties recur in a great- 

 ly augmented degree. 



We have thus already come within sight of a conclusion, which the prog- 

 ress of the inquiry will, I think, bring before us with the clearest evi- 

 dence : namely, that in the sciences which deal with phenomena in which 

 artificial experiments are impossible (as in the case of astronomy), or in 

 which they have a very limited range (as in mental philosophy, social 

 science, and even physiology), induction from direct experience is practiced 

 at a disadvantage in most cases equivalent to impracticability ; from which 

 it follows that the methods of those sciences, in order to accomplish any 

 thing worthy of attainment, must be to a great extent, if not principally, 



