With this doctrine,that of cost of production as determining price collapses,and the principle emerges that it is not cost ofproduction,but demand and supply,on which domestic,no less than international,values depend,though this formula willrequire much interpretation before it can be used safely and with advantage.Thus Leslie extends to the whole of the nationalindustry the partial negation of the older dogma introduced by Cairnes through the idea of non-competing groups.He doesnot,of course,dispute the real operation of cost of production on price in the limited area within which rates of profit andwages are determinate and known;but he maintains that its action on the large scale is too remote and uncertain to justifyour treating it as regulator of price.Now,if this be so,the entire edifice which Ricardo reared on the basis of the identity ofcost of production and price,with its apparent but unreal simplicity,symmetry,and completeness,disappears;and theground is cleared for the new structure which must take its place.Leslie predicts that,if political economy,under that name,does not bend itself to the task of rearing such a structure,the office will speedily be taken out of its hands by Sociology.
Leslie was a successful student of several special economic subjectsof agricultural economy,of taxation,of the distributionof the precious metals and the history of prices,and,as has been indicated,of the movements of wages.But it is in relationto the method and fundamental doctrines of the science that he did the most important,because the most opportune andneedful work.And,though his course was closed too early for the interests of knowledge,and much of what he producedwas merely occasional and fragmentary,his services will be found to have been greater than those of many who have leftbehind them more systematic,elaborate,and pretentious writings.
