INDUCTION. 



inquire, or try to observe, what had been done to the arrows in 

 particular instances. 



Wherever, having nothing to guide us to the cause, we 

 are obliged to set out from the effect, and to apply the rule of 

 varying the circumstances to the consequents, not the antece- 

 dents, we are necessarily destitute of the resource of artificial 

 experimentation. We cannot, at our choice, obtain conse- 

 quents, as we can antecedents, under any set of circumstances 

 compatible with their nature. There are no means of pro- 

 ducing effects but through their causes, and by the supposi- 

 tion the causes of the effect in question are not known to us. 

 We have therefore no expedient but to study it where it 

 offers itself spontaneously. If nature happens to present us 

 with instances sufficiently varied in their circumstances, and if 

 we are able to discover, either among the proximate ante- 

 cedents or among some other order of antecedents, something 

 which is always found when the effect is found, however 

 various the circumstances, and never found when it is not; 

 we may discover, by mere observation without experiment, a 

 real uniformity in nature. 



But though this is certainly the most favourable case for 

 sciences of pure observation, as contrasted with those in which 

 artificial experiments are possible, there is in reality no case 

 which more strikingly illustrates the inherent imperfection of 

 direct induction when not founded on experimentation. Sup- 

 pose that, by a comparison of cases of the effect, we have 

 lound an antecedent which appears to be, and perhaps is, 

 invariably connected with it : we have not yet proved that 

 antecedent to be the cause, until we have reversed the process, 

 and produced the effect by means of that antecedent. If we 

 can produce the antecedent artificially, and if, when we do so, 

 the effect follows, the induction is complete ; that antecedent 

 is the cause of that consequent.* But we have then added 



* Unless, indeed, the consequent was generated not by the antecedent, but 

 by the means employed to produce the antecedent. As, however, these 

 means are under our power, there is so far a probability that they are also 

 sufficiently within our knowledge, to enable us to judge whether that could be 

 the case or not. 



