OBSERVATION AND EXPERIMENT. 219 



of known circumstances, the plienomena which nature exhibits on a 

 grander scale uncUn- the form of lii^hrniniT and thunder. Now let any 

 one consider wirat amount of kiu)wled'u;e ot'riie etfects and laws of elec- 

 tric agency mankind could ever have obtained from the mere observation 

 of thunder-storms, and compare it with that which they have gained, 

 and may expect to gain, from electrical and galvanic experiments. 

 This example is the more striking, now that we have reason to believe 

 that electric action is of all natural phenomena (except heat) the most 

 pervading and universal, which, therefore, it might antecedently have 

 been supposed could stand least in need of artificial means of produc- 

 tion to enable it to be studied ; while the fact is so much tlie contrary, 

 that without the electric machine, the voltaic l?attery, and the Leyden 

 jar, we should never have suspected tile existence of electricity as one 

 of the great agents in nature ; the few electric phenomena we should 

 have known of would have continued to be regarded either as super- 

 natural, 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 

 produce 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 phenomenon behaves under an indefinite variety of possible 

 circumstances. Thus, chemists, after having obtained some newly-dis- 

 covered substance in a pure state, (that is, having made sure that there 

 is nothing present whicn can interfere with and modify its agency,) 

 introduce various other substances, one by one, to ascertain whether it 

 will combine with them, or decompose 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 phe- 

 nomenon, and we have to seek for instances in which nature produces 

 it, the task before us is one of quite another kind. Instead of being 

 able to choose what thq concomitant circumstances shall be, we now 

 have to discover what they are ; which, when we go beyond the sim- 

 plest and most accessible cases, it is next to impossible to do, with any 

 precision and completeness. Let us take, as an exemplification of a phe- 

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

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

 able to produce it 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 connexion with it, also 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 exploration. If, instead of a human 

 mind, we suppo.se the subject of investigation to be a human society 

 or State all the same difficulties recur in a greatly augmented degree. 



