THE CHEMICAL METHOD. 469 



cient variation of circumstances, an induction from specific 

 experience is attainable ; otherwise not. The question to be 

 resolved is, therefore, whether the requisites for induction 

 respecting the causes of political effects or the properties of 

 political agents, are to be met with in history ? including 

 under the term, cotemporary history. And in order to give 

 fixity to our conceptions, it will be advisable to suppose this 

 question asked in reference to some special subject of political 

 inquiry or controversy ; such as that frequent topic of debate 

 in the present century, the operation of restrictive and prohi 

 bitory commercial legislation upon national wealth. Let this, 

 then, be the scientific question to be investigated by specific 



experience, 



. - &quot;\ \ i 



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 parti 

 cular 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, spontaneous and acquired ; whose 

 habits, usages, opinions, laws and institutions are the same in 

 all respects, except that one of them has a more protective 

 tariff, or in other respects interferes more with the freedom of 

 industry ; if one of these nations is found to be rich, and the 

 other poor, or one richer than the other, this will be an expe- 

 rimentum crucis : a real proof by experience, which of the 

 two systems is most favourable to national riches. But the 

 supposition thatjtwo such instances can be met with is mani- 

 festly_absiirjL _Nor_is such_ a concurrence^~evennrbstracte^^ 

 possible-^ Two_jnations whichJagree3 j in__eYerYthing 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 pre-existing 

 causes. If the two nations differ in this portion of their in 

 stitutions, 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 



