in 1931, Hayek crititicized John Maynard Keynes's Treatise on Money (1930) in his "Reflections on the pure theory of Mr. J.M. Keynes"[124] and published his lectures at the LSE in book form as Prices and Production.[125] For Keynes, unemployment and idle resources are caused by a lack of effective demand, but for Hayek they stem from a previous unsustainable episode of easy money and artificially low interest rates.