Controversy Between Keynes and the "Classics": the Origin of Macroeconomics

The fundamental difference between the theory of Keynes and that of the Classics is as follows: the theory of the Classics is about barter economy in which money hasn't any function while the theory of Keynes is about money economy in which money has a decisive role.Keynes emphasized the uncertain nature of money economy and introduced the value reserve function of money to construct theory of liquidity preference,which built a channel between money and effective demand and hence provided an analytic framework of national income determination for the serious study of macroeconomics.