162 Professor Whewell on the 



eminent philosopher. And if it were to be maintained, for in- 

 stance, that the rate of increase varies inversely as the existing 

 population of a given district, or if any other mathematical law 

 were asserted ; though the probabilities against it would be so 

 strong, as only to be surmountable by an enormous mass of 

 evidence; the law itself might easily be made to attract notice 

 with the pretensions of a discovery. 



The following is the manner in which the Postulate now 

 under notice is introduced into calculation. 



Let w be the wages of a labourer for one year, when the price 

 of corn is p, Let a fraction / of the labourer's wages be ex- 

 pended in corn (or other necessary food), and the remaining frac- 

 tion \-f in other commodities which do not rise in price with 

 corn. Now let the price of corn become p(l+x). Then the ex- 

 penditure of the labourer will be (1 + x)fw for corn, and (1 -f) w, 

 as before, for other things. Therefore the whole wages are now . 



= (1 + x\fw + (1 -/) w = (1 +/*) w - 



III. Postulate of Price. 



5. The exchangeable value of a commodity depends solely 

 upon the relative quantity of labour necessary for its production. 

 Or, in other words, articles which require for their production 

 equal quantities of labour will exchange for each other. 



It is not difficult to shew that all exchangeable value has its 

 source in human labour; and that this is true of raw produce 

 no less than of manufactured goods. Mr. Ricardos principle 

 goes further, and asserts that the exchangeable value is in pro- 

 portion to the quantity of the labour necessarily employed, with- 

 out any regard to the wages which have been paid ; the capital 

 by which the labour is aided being however estimated as part of 



