Much of undergraduate macroeconomic theory is discussed on the assumption that, in the short run, the expectations of economic agents about the future values of macroeconomic variables are given. The rationale for this treatment of expectations in macroeconomic theory can be derived fiom Keynes' views on the nature of expectations, including his discussion in the General Theory. While Keynes' views on the nature of uncertainty and expectations form the basis for the writings of many Post-Keynesian economists, most of modern macroeconomic theory treats uncertainty and expectations in a radically different manner.