552 LOGIC OF THE MORAL SCIENCES. 



great topic of debate in the present day, the operation of restrictive and 

 prohibitory commercial legislation upon national wealth. Let this, then, 

 be the scientific question to be investigated by specific experience. 



§ 3. In order to apply to the case the most perfect of the methods 

 of experimental inquiry, the Method of Difference, we require to find 

 two instances, which tally in every particular except the one which is 

 the subject of inquiry. If two nations can be found which are alike in 

 all natural advantages and disadvantages ; whose people resemble each 

 other in every quality, physical and moral, innate and acquired ; whose 

 habits, usages, opinions, laws, and institutions are the same in all re- 

 spects, except that one of them has a more protective tariff, or in other 

 respects interferes more with the fieedom of industry ; and if one of 

 these nations is found to be rich, and the other poor, or one richer 

 than the other, this will be an experhnentum crucis: a real proof, by 

 experience, which of the two systems is most favorable to national 

 riches. But the supposition that two such instances can be met with 

 is absurd on the face of it. Nor is such a concurrence even abstract- 

 edly possible. Two nations which agreed in everything except their 

 commercial policy would agree also in that. Differences of legislation 

 are not inherent and ultimate diversities ; are not properties of Kinds. 

 They are effects of preexisting causes. If the two nations differ in 

 this pr)rtion of their institutions, it is from some difference in their 

 position, and thence in their apparent interests, or in some portion or 

 other of their opinions, habits, and tendencies ; which opens a view of 

 further differences without any assignable limit, capable of operating 

 on their industrial prosperity, as well as on every other feature of their 

 condition, in more ways than can be enumerated or imagined. There 

 is thus a demonstrated impossibility of obtaining, in the investigations 

 of the social science, the conditions required for the most conclusive 

 forai of inquiry by specific experience. 



In the absence of the direct, we may next try, as in other cases, the 

 supplementary resource, called in a fonner place the Indirect Method 

 of Difference: which, instead of two instances differing in nothing but 

 the presence or absence of a given circumstance, compares two classes 

 of instances respectively agreeing in nothing but the presence of a cir- 

 cumstance on the one side and its absence on the other. To choose 

 the most advantageous case conceivable (a case far too advantageous 

 to be ever obtained), suppose that we compare one nation which has a 

 restrictive policy, with two or more nations agi-eeing in nothing but in 

 permitting free trade. We need not now suppose that either of these 

 nations agrees with tlje first in all its circumstances ; one may agree 

 with it in some of its circumstances, and another in the remainder. 

 And it may be argued, that if these nations remain poorer than 

 the restrictive nation, it cannot be for want either of the first or of the 

 second set of circumstances, but it must be for want of the protecting 

 system. If (we might say) the restrictive nation had prospered from 

 the one set of causes, the first of the free-trade nations would have 

 prospered equally ; if by I'eason of the other, the second would : but 

 neither has: therefore the prosperity was owing to the restrictions. 

 This will be allowed to be a very favorable specimen of an argument 

 from specific experience in politics, and if this be inconclusive, it would 

 not be easy to find another preferable to it. 



