Treated at first as a doctrine peculiarly applicable to land, with a certain controverted relevance to other natural agents, it has been so extended that there is scarcely any subject of economic study in which we may not expect to find adaptations or analogies, so that Ricardo seemed to have discovered the key of economic knowledge.
Economics is unlike many other sciences in the fact that its claim to recognition must be based upon its practical utility, on its relevance to the actual life of the economic world, on its ability to unravel the social and economic difficulties of each generation, and to contribute to the progress of nations.
Their achievements in the r9th century will be fully acknowledged, but the relevance of their work to the problems of the zoth century will be admitted less than at the present time.
If we add the qualification of relevance we destroy the cogency of the method.
It is not so easy to determine their relevance and usefulness in relation to distinctively modern problems, or to indicate within what limits their work is of permanent value, and we can only deal with these questions in their more general aspects.
At any rate, if relevance in proximo is interpolated in the peccant clause of the canon of the Joint-Method, the practical utility of the method is rehabilitated.
The claim of economics for recognition as a science and as a subject of study must be based on its relevance to the actual life of the economic world, on its ability to unravel the practical difficulties of each generation, and so contribute to the progress of nations.
It is extremely important to consider how far the economic conceptions based upon this view of the action of men in the ordinary business of lif e - such, for example, as the doctrine of marginal utility - depend for their truth and relevance on the fact that in economics we are dealing with large aggregates.