logic behind the simple supply curve is wrong when it is applied to the relationship between aggregate supply and the price level. Part of teaching economics is teaching economic reasoning.Our discipline is built around deductive logic.Once we teach students a pattern of logic,we want and expect them to apply it to new circumstances.When they apply the logic of a simple demand curve or a simple supply curve to the aggregate demand or aggregate supply curve,the logic does not fit.We believe that the best way to teach the reasoning embodied in the aggregate demand and aggregate supply curves without creating confusion for students is to build up to those topics carefully.