The following study is the outgrowth of investigations in the "Quantity Theory" of money, carried on in the seminar of Professor Jesse E. Pope, at the University of Missouri, during the term 1904-5. That a satisfactory general theory of value must underlie any adequate treatment of the problem of the value of money, and that there is little agreement among monetary theorists concerning the general theory of value, became very evident in the course of this investigation; and that the present writer's conception of value, as expressed in a paper written at that time on the "Quantity Theory," was not satisfactory, became painfully clear after Professor Pope's kindly but fundamental criticisms. The problem of value, laid aside for a time, forced itself upon me in the course of my teaching: my students seemed to understand the treatment of value in the text-books used quite clearly, but I could never convince myself that I understood it, and the conviction grew upon me that the value problem really remained unsolved. Hence the present book. It was begun in Dean Kinley's seminar, at the University of Illinois, in the term 1909-10. The first three parts, in substantially their present form, and an outline sketch of the germ idea of the fourth part, were submitted, in May of 1910, in the Hart, Schaffner & Marx Economic Prize Contest of that year. Part IV was elaborated in detail, and minor changes made in the first three parts, during the year 1910-11, at Columbia University. The book is submitted as a doctor's dissertation to the Faculty of Political Science of that institution. My obligations to others in connection with this book are numerous. I cannot refrain from thanking my old teacher Professor Pope, in this connection. I owe my interest in economic theory, and the greater part of my training in economic method, to the three years I spent in his seminar at Missouri. I am also indebted to him for substantial aid in the critical revision of the proofsheets. At the University of Illinois, Dean Kinley and Professors E. L. Bogart and E. C. Hayes were of special service to me, as was also Mr. F. C. Becker, now of the department of philosophy at the University of California. Dean Kinley, in particular, criticized several successive drafts, and made numerous valuable suggestions. My chief obligations at Columbia University are to Professors Seligman, Seager, John Dewey, and Giddings. My debt to Professors Seligman and Dewey is, in part, indicated in the course of the book, so far as points of doctrine are concerned. Both have been kind enough to read and criticize the provisional draft, and Professor Seligman has supervised the revision at every stage. My wife's services, in criticism, in bibliographical work, and in the mechanical labors which writing a book involves, have been indispensable.