The theory of the value of money is a special case of the general theory of economic value. To the layman, this would seem to go without saying. To the student of the literature of the subject, however, who has noticed the wide divergence between the method of approach to the general problem of value and the method of approach to the problem of the value of money, in most treatises which include both these topics, the proposition will sound unusual if not heretical. Most text-books in English to-day will offer the marginal utility theory as the general theory of value. The same books commonly present the quantity theory of the value of money. Whether or not the two theories are consistent may wait for later discussion, but that the quantity theory of money is a _deduction from_ the utility theory of value, and a _special case_ of the utility theory of value, will not, I believe, be contended by anyone. Certainly in its origin, the quantity theory is much the older theory. The same is true for those writers who seek to explain value in general on the basis of cost of production, and who at the same time offer the quantity theory to explain the value of money. The two theories may or may not be consistent, but in any case, they are logically and historically independent, neither being a deduction from the other. Older writers (as Walker and Mill), whose treatment of the general theory of value runs in terms of "supply and demand," have stated that the quantity theory is merely a special case of the law of supply and demand, and the statement is occasionally met in present-day writings, though one of the most recent and best known of the expositions of the quantity theory, Professor Fisher's _Purchasing Power of Money_, very explicitly repudiates this doctrine.[41] But it may be easily shown, and will be shown later, that the quantity theory, and the present-day formulation of the law of supply and demand, are in no way logically dependent upon each other. This lack of connection between two bodies of doctrine which should be in a most intimate and essential way related to each other, may well throw suspicion on the current treatments of both topics. In any case the lack of connection raises a problem, and calls for explanation.