A break in Keynes's theory of interest

In his recent book, The General Theory of Employment, Interest, and Money, John Maynard Keynes develops the idea that interest is not determined, as traditional theory assumes, by the will to save and the will to consume, but by the "liquidity preference" of the investor. At the same time Keynes assumes that efficiency of capital declines with increase in the amount of capital. This assumption, justified in itself and an indispensable part of Keynes's theory, has implications which are incompatible with the "liquidity-preference" theory of interest; they require an explication of interest as the equilibrating force between saving and consumption, and thus the acceptance of the "orthodox" theorem which Keynes meant to refute.