As intimated above, the notion that if the labourer receives compensation according to his product he receives just compensation, is one of the most prevalent and fundamental concepts in the controversy about wage justice. Hence we find it in certain theories which reject the doctrine of the right to the whole product. According to these theories, not only the labourer but all the agents of production should be rewarded in proportion to their productive contributions. Instead of the whole product, the worker ought to receive that portion of it which corresponds to his specific productivity, that is, that portion of the product which represents his productive influence as compared with the productive efficacy of land, capital, and business energy. _Clark's Theory of Specific Productivity_ One of the theories referred to in the last paragraph is that which has been elaborated in great detail and with great ingenuity by Professor John Bates Clark. As stated by himself in the opening sentence of the preface to his "Distribution of Wealth," its main tenet is, "that the distribution of the income of society is controlled by a natural law, and that this law, if it worked without friction, would give to every agent of production the amount of wealth which that agent creates." In a régime of perfect competition, therefore, the labourer would get, not the whole product of industry, but the whole product due to his own exertions. It is impossible, and indeed unnecessary, to enter upon an extended examination of this contention. It will be sufficient to state in a summary way the most obvious and cogent objections. Without making any examination of Professor Clark's theory, we should expect to find it unconvincing. For the productive process is by analogy an organic process, in which every factor requires the co-operation of every other factor in order to turn out even the smallest portion of the product. Each factor is in its own order the cause of the whole product. Consequently no physical portion of the product can be set aside and designated as wholly due to any one factor. Can we not, however, distinguish the _proportionate productive influence_ exerted by each factor, and the proportion of the product which represents such productive influence? This is the question to which Professor Clark addresses himself with much ingenuity, subtlety, and labour, and to which he returns an affirmative answer.[235]