Situation before the publication of Keynes' General Theory, 488.— New controversial issues, 488.— I. Rates of return on economic resources: securities, 490; cash, 492; production, 493; consumption, 494.— Nature of the rates of return, 495.—II. Fundamentals of economic behavior: individuals, 496; firms, 496; banks, 497; governments, 498.— Significance of an arbitrary monetary policy, 498.— III. The theory of interest: the marginal productivity theory, 500; the time-preference theory, 501; the liquidity-preference theory, 503; the loanable-funds theory, 505. — Validity of the theories of interest, 506.