32. The relation between the volume of money and the volume of credit is exceedingly flexible. The relation between the world's volume of credit and the world's volume of gold is likewise exceedingly loose, uncertain, and flexible. (Chapters on "Volume of Money and Volume of Credit," and "The Quantity Theory and World Prices.")
33. "Velocity of circulation" is a blanket name for a complex and heterogenous set of activities of men. It is a passive resultant of many causes, and is itself a cause of nothing. The safest generalization possible concerning it is that it varies with the volume of trade and with prices.
34. Barter remains an important factor in modern economic life, and is a flexible substitute for the use of checks and money, increasing when the money market "tightens." It is greatly facilitated by the "common measure of values" function of money.
35. The general criticism of the mechanistic scheme of causation involved in the quantity theory has, as its positive corollary, the doctrine that psychological explanations must be given—that the phenomena are intricate and complex, as intricate and complex as the play of human ideas and emotions, and the network of social relationships.
36. This means that the theory of value, and of the value of money, as here presented, cannot assume the simple form, or the mathematical precision, which have made the quantity theory so alluring. It means, further, that the present study, as in part pioneer work, will lack finish and definiteness in many places, will contain errors and gaps, and will leave many problems unsolved, and many distinctions undrawn. At many points, the analysis is confessedly incomplete, and the problems imperfectly thought through—often inadequately stated, if seen at all.
In what follows, these theses, with doctrines yet to be developed, will be woven together into a systematic theory of money and credit.
The study of the functions of money, in relation to its value, will best be approached, I think, through a study of the origin of money. In this, I shall base my conclusions chiefly on the work of Karl Menger and W. W. Carlile, who seem to me to have done most in this field.
On the basis of the general theory of value developed in the first chapter, and the results of the two chapters which are to follow on the origin and functions of money, I shall reach my main conclusions as to the laws of the value of money. On the basis of this theory of value, and of the theory of the functions of money, I shall also try to develop a psychological theory of credit, and to assimilate credit phenomena to the general phenomena of value. The development which the theory of credit has had, at the hands of men whose chief interest was that of the jurist or accountant, is valuable and important. I do not wish to discredit what has been done. Many important doctrines concerning credit have been developed. The general theory of elastic bank-credit, worked out in the controversy between the "Currency" and the "Banking" Schools, is of the highest importance. This theory I have discussed in the chapter on "The Volume of Trade and the Volume of Money and Credit." I still feel, however, that there are gaps in the prevailing ideas on credit which only a social psychology can fill. I shall undertake to construe credit as a part of the social system of motivation and control, and to differentiate it from other parts of that system by an analysis of its functions. I think, too, that the theory of the relation of credit and money is in especially unsatisfactory shape, particularly with reference to the factors governing reserves.
A final chapter, in Part IV, will undertake to bring together the various points in our discussion which deal with the theory of prosperity, and will seek to bring the notions of "theory of prosperity vs. theory of wealth," "statics vs. dynamics," "normal vs. transitional tendencies," and certain other similar contrasts, into a higher synthesis, which will, to be sure, not rob these contrasts of their significance, but will rather find certain generic principles which they share, and so make it possible to measure considerations in one sphere in terms of considerations in the other sphere. In very large degree, students of dynamics and students of statics have been talking at cross-purposes, missing the force of one another's arguments, and have been quite unable, even when understanding one another, to come to agreement, precisely because they have lacked principles by means of which they could compare in any quantitative way the forces which each studies. A higher synthesis, which would give static and dynamic theories common ground, would seem to be a desideratum of high importance. Such a synthesis would go far toward unifying the science of economics. I believe that the theory of money and credit, approached from the angle of the social value theory, will meet this need.