 Pause and reflect on how difficult it would be to discern inflation in the early modern period, or perhaps even at present, and thus how brilliant was the insight that the overall price level is a function of the money supply. In the 1520s, the Prussian Diet commissioned none other than Nicholas Copernicus to investigate the recent increase in price instability. Drawing on his skills with handling large quantities of data, Copernicus’s Monetae cudendae ratio (1526) established the proposition that the value of the currency (its purchasing power) had diminished due to its abundance. We thus have the first inkling of a principle that is, in some respects, as central to economics as the principle of inertia is in physics.