The economic laws aimed at and formulated under the guidance of this preconception are laws of what takes place "naturally" or "normally," and it is of the essence of things so conceived that in the natural or normal course there is no wasted or misdirected effort. The standpoint is given by the material interest of mankind, or, more concretely, of the community or "society" in which the economist is placed; the resulting economic theory is formulated as an analysis of the "natural" course of the life of the community, the ultimate theoretical postulate of which might, not unfairly, be stated as in some sort a law of the conservation of economic energy. When the course of things runs off naturally or normally, in accord with the exigencies of human welfare and the constraining laws of nature, economic income and outgo balance one another. The natural forces at play in the economic field may increase indefinitely through accretions brought in under man's dominion and through the natural increase of mankind, and, indeed, it is of the nature of things that an orderly progress of this kind should take place; but within the economic organism, as within the larger organism of the universe, there prevails an equivalence of expenditure and returns, an equilibrium of flux and reflux, which is not broken over in the normal course of things. So it is, by implication, assumed that the product which results from any given industrial process or operation is, in some sense or in some unspecified respect, the equivalent of the expenditure of forces, or of the effort, or what not, that has gone into the process out of which the product emerges. This theorem of equivalence is the postulate which lies at the root of the classical theory of distribution, but it manifestly does not admit of proof--or of disproof either, for that matter; since neither the economic forces which go into the process nor the product which emerges are, in the economic respect, of such a tangible character as to admit of quantitative determination. They are in fact incommensurable magnitudes. To this last remark the answer may conceivably present itself that the equivalence in question is an equivalence in utility or in exchange value, and that the quantitative determination of the various items in terms of exchange value or of utility is, theoretically, not impossible; but when it is called to mind that the forces or factors which go to the production of a given product take their utility or exchange value from that of the product, it will easily be seen that the expedient will not serve. The equivalence between the aggregate factors of production in any given case and their product remains a dogmatic postulate whose validity cannot be demonstrated in any terms that will not reduce the whole proposition to an aimless fatuity, or to metaphysical grounds which have now been given up.