It is not possible to indicate more than generally the special advances in economic doctrine effected by him, but the following points may be noted as establishing for him a claim to a place beside Ricardo and Mill. Cairnes' exposition of the province and method of political economy: He never suffers it to be forgotten that political economy is a science, and consequently that its results are entirely neutral with respect to social facts or systems. It has simply to trace the necessary connections among the phenomena of wealth and dictates no rules for practice. Further, he is distinctly opposed both to those who would treat political economy as an integral part of social philosophy, and to those who have attempted to express economic facts in quantitative formulae and to make economy a branch of applied mathematics. According to him political economy is a mixed science, its field being partly mental, partly physical. It may be called a positive science, because its premises are facts, but it is hypothetical in so far as the laws it lays down are only approximately true, i.e. are only valid in the absence of counteracting agencies. From this view of the nature of the science, it follows at once that the method to be pursued must be that called by Mill the physical or concrete deductive, which starts from certain known causes, investigates their consequences and verifies or tests the result by comparison with facts of experience. It may, perhaps, be thought that Cairnes gives too little attention to the effects of the organism of society on economic facts, and that he is disposed to overlook what Walter Bagehot called the postulates of political economy. Cairnes' analysis of cost of production in its relation to value: According to Mill, the universal elements in cost of production are the wages of labour and the profits of capital. To this theory Cairnes objects that wages, being remuneration, can in no sense be considered as cost, and could only have come to be regarded as cost in consequence of the whole problem being treated from the point of view of the capitalist, to whom, no doubt, the wages paid represent cost. The real elements of cost of production he looks upon as labour, abstinence and risk, the second of these falling mainly, though not necessarily, upon the capitalist. In this analysis he to a considerable extent follows and improves upon Nassau William Senior, who had previously defined cost of production as the sum of the labour and abstinence necessary to production. Cairnes' exposition of the natural or social limit to free competition, and of its bearing on the theory of value: He points out that in any organised society there can hardly be the ready transference of capital from one employment to another, which is the indispensable condition of free competition; while class distinctions render it impossible for labour to transfer itself readily to new occupations.