The divide between Ludwig von Mises and John Maynard Keynes is not merely a disagreement over policy, but a deeper conflict about the nature of economic reality itself. Mises—building on the tradition of Jean-Baptiste Say—understands the economy as an intertemporal process, where production, savings, and investment must be aligned through genuine price signals, especially the interest rate. Keynes, by contrast, compresses economic time into a short-run framework in which aggregate demand becomes the central variable, and monetary expansion is recast from a source of distortion into a tool of