Moreover, it is inadequate as a measure of justice. Should the majority of both employers and employés fix the "economic value" of the labour of carpenters at five dollars a day, there would be no certainty that this decision was correct, and that this figure represented just wages. Should they determine upon a rate of fifty dollars a day, we could not be sure that their decision was unjust. Undoubtedly the combined judgment of employers and employés will set a fairer wage than one fixed by either party alone, since it will be less one-sided; but there is no sufficient reason for concluding that it will be in all cases completely just. Undoubtedly employers and employés know what wages an industry can afford at prevailing prices, on the assumption that business ability and capital are to have a certain rate of return; but there is no certainty that the prevailing prices are fair, or that the assumed rates of profits and interest are fair. In a word, the device is too arbitrary. To sum up the entire discussion of exchange-equivalence theories: Their underlying concept is fundamentally unsound and impracticable. All of them involve an attempt to compare two entities which are utterly incommensurate. There exists no third term, or standard, or objective fact, which will inform men whether any rate of wages is the equivalent of any quantity of labour. III. PRODUCTIVITY THEORIES The productivity concept of wage justice appears in a great variety of forms. The first of them that we shall consider is advocated mainly by the Socialists, and is usually referred to as the theory of the "right to the whole product of labour."[224] _Labour's Right to the Whole Product_ We have seen that Adam Smith's belief in the normality and beneficence of free competition would have logically led him to the conclusion that competitive wages were just; and we know that this doctrine is implicit in his writings. On the other hand, his theory that all value is determined by labour would seem to involve the inference that all the value of the product belongs to the labourer. As a matter of fact, Smith restricted this conclusion to primitive and pre-capitalist societies. Apparently he, and his disciples in an even larger degree, was more interested in describing the supposed beneficence of competition than in justifying the distribution that resulted from the competitive process.