Allgemeine Theorie der Beschäftigung, des Zinses und des Geldes
John Maynard Keynes criticized the quantity theory of money in his book "The General Theory of Employment, Interest and Money". Keynes had originally been a proponent of the theory, but he presented an alternative in the "General Theory". Keynes argued that the price level was not strictly determined by the money supply. Changes in the money supply could have effects on real variables like output.