Hence the curious phenomenon that very much of static theory has been developed in abstraction from _money_ and _credit_. Mill's theory of international values, for example, abstracts from money. "Since all trade is in reality barter, money being a mere instrument for exchanging things against one another, we will, for simplicity, begin by supposing the international trade to be in form, what it is in reality, an actual trucking of one commodity against another. So far as we have hitherto proceeded, we have found the laws of interchange to be essentially the same, whether money is used or not; money never governing, but always obeying, those general laws."[299] Other writers have similarly held that money is a mere cloak, covering up the reality of the economic process. Schumpeter, for example, holds that money is, in the static analysis, merely a "Schleier," and that "man nichts Wesentliches uebersicht, wenn man davon abstrahiert."[300] _On the static assumptions_, of the fluid market, with friction, etc., banished, money is, indeed, anomalous and inexplicable. It is a cloak, a complication, a vexatious "epi-phenomenon." There is nothing for it to do, and there can be, consequently, no "functional theory" developed for it. Static theory may be ungracious in ignoring its own foundation. But static theory is grotesque when it seeks to support its own foundation! Static theory is possible only on the assumption that the work of money and credit has been done. What, then, shall we say of static theory which seeks to explain the work of money and credit? Yet precisely this is what is undertaken by the quantity theory, with its "normal" or "static" laws of money and credit. A functional theory of money and credit must be a dynamic theory. To talk about the laws of money, "after the transition is completed" is to talk about the work money will do after it has finished working. For a functional theory of money and credit, we must study the obstacles that exist to prevent the fluid market. We must study friction, transitions, dynamic phenomena. To this problem we shall come in Part III. For the present, I am content to have disproved the quantity theory contention that the volume of trade is independent of the quantity of money and credit. APPENDIX TO CHAPTER XIII THE RELATION OF FOREIGN TO DOMESTIC TRADE IN THE UNITED STATES[301]