OBSERVATION AND EXPERIMENT. 



251 



made sure that there is nothing pre- 

 sent which can interfere with and 

 modify its agency,) introduce various 

 other substances, one by one, to ascer- 

 tain 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 pheno- 

 menon, and we have to seek for in- 

 stances 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 

 beyond the simplest and most acces- 

 sible cases, it is next to impossible to 

 do with any precision and complete- 

 ness. Let us take, as an exemplifica- 

 tion 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 unascertain- 

 able 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 com- 

 plication of physical facts, in no two 

 cases perhaps exactly similar, and 

 most of which (except the mere struc- 

 ture, 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 suppose the sub- 

 ject of investigation to be a human 

 society or itate, all the same difficul- 

 ties recur in a greatly augmented 

 degree. 



We have thus already come within 



sight of a conclusion which the pro- 

 gress 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 practised at a dis- 

 advantage in most cases equivalent to 

 impracticability : from which it fol- 

 lows that the methods of those sciences, 

 in order to accomplish anything wor- 

 thy of attainment, must be to a great 

 extent, if not principally, deductive. 

 This is already known to be the case 

 with the first of the sciences we have 

 mentioned, astronomy ; that it is not 

 generally recognised as true of the 

 others is probably one of the reasons 

 why they are not in a more advanced 

 state. 



§ 4. If what is called pure observa- 

 tion is at so great a disadvantage, 

 compared with artificial experimenta- 

 tion, in one department of the direct 

 exploration of phenomena, there is 

 another branch in which the advan- 

 tage is all on the side of the former. 



Inductive inquiry having for its ob- 

 ject to ascertain what causes are con- 

 nected with what effects, we may begin 

 this search at either end of the road 

 which leads from the one point to the 

 other : we may either inquire into the 

 effectsofagivencause,orintothecau8es 

 of a given effect. The fact that light 

 blackens chloride of silver might have 

 been discovered either by experiments 

 on light, trying what effect it would 

 produce on various substances, or by 

 observing that portions of the chloride 

 had repeatedly become black, and in- 

 quiring into the circumstances. The 

 effect of the urali poison might have 

 become known either by administer- 

 ing it to animals, or by examining 

 how it ha.ppened that the wounds 

 which the Indians of Guiana inflict 

 with their arrows prove so uniformly 

 mortal. Now it is manifest from the 



