THE DEDUCTIVE METHOD. 325 



the new cause becomes conspicuous enough to be a subject of induction, so 

 many of the other influencing circumstances will have changed as to vitiate 

 the experiment.* 



Two, therefore, of the three possible methods for the study of phenomena 

 resulting from the composition of many causes, being, from the very nature 

 of the case, inefiicient and illusory, there remains only the third — that which 

 considers the causes separately, and infers the effect from the balance of 

 the different tendencies which produce it: in short, the deductive, or a pri- 

 ori method. The more particular consideration of this intellectual process 

 requires a chapter to itself. 



CHAPTER XI. 



OF THE DEDUCTIVE METHOD. 



§ 1. The mode of investigation which, from the proved inapplicability 

 of direct methods of observation and experiment, remains to us as the 

 main source of the knowledge we possess or can acquire respecting the 

 conditions and laws of recurrence, of the more complex phenomena, is 

 called, in its most general expression, the Deductive Method ; and consists 

 of three operations: the first,one of direct induction; the second, of ra- 

 tiocination ; the third, of verification. 



I call the first step in the process an inductive operation, because there 

 must be a direct induction as the basis of the whole ; though in many par- 

 ticular investigations the place of the induction may be supplied by a prior 

 deduction ; but the premises of this prior deduction must have been de- 

 rived from induction. 



■** The problem of the Deductive Method is, to find the law of an effect, 

 from the laws of the different tendencies of which it is the joint result. 

 The first requisite, therefore, is to know the laws of those tendencies ; the 

 law of each of the concurrent causes : and this supposes a previous proc- 

 ess of observation or experiment upon each cause separately ; or else a pre- 

 vious deduction, which also must depend for its ultimate premises on ob- 

 servation or experiment. Thus, if the subject be social or historical phe- 

 nomena, the premises of the Deductive Method must be the laws of the 

 causes which determine that class of phenomena ; and those causes are hu- 

 man actions, together with the general outward circumstances under the 



* Professor Bain, though concurring generally in the views expressed in this chapter, seems 

 to estimate more highly than I do the scope for specific experimental evidence in politics. 

 {Logic, ii., 333-337.) There are, it is true, as he remarks (p. 336), some cases "when an 

 agent suddenly introduced is almost instantaneoush' followed by some other changes, as when 

 the announcement of a diplomatic rupture between two nations is followed the same day by a 

 derangement of the money-market." But this experiment would be quite inconclusive merely 

 as an experiment. It can only serve, as any experiment may, to verify the conclusion of a 

 deduction. Unless we already knew by our knowledge of the motives which act on business 

 men, that the prospect of war tends to derange the money-market, we should never have been 

 able to prove a connection between the two facts, unless after having ascertained historically 

 that the one followed the other in too great a number of instances to be consistent with their 

 having been recorded with due precautions. Whoever has carefully examined any of the at- 

 tempts continually made to prove economic doctrines by such a recital of instances, knows 

 well how futile they are. It always turns out that the circumstances of scarcely any of the 

 cases have been fully stated ; and that cases, in equal or greater numbers, have been omitted 

 which would have tended to an opposite conclusion. 



