In The General Theory, John Maynard Keynes broke with the quantity theory of money, not just in working out a monetary theory of production but, as he says, in arguing the case for a monetary theory of value. Keynes writes (CW, 7, pp. xxii-xxiii):A monetary economy, we shall find, is essentially one in which changing views about the future are capable of influencing the quantity of employment and not merely its direction. But our method of analyzing the economic behaviour of the present under the influence of changing ideas about the future is one which depends on the interaction of supply and demand, and is in this way linked up with our fundamental theory of value. We are thus led to a more general theory, which includes the classical theory with which we are familiar, as a special case.
