The course focuses on the development of monetary theories during the XX century, through the readings of original texts. The first part of the course is dedicated to John Maynard Keynes, starting from the Treatise on Money and following with the General Theory and his project of “International Clearing Union”. Successively, Milton Friedman’s contributions and the revival of “quantitative theory” and the strong criticism proposed by Kaldor will be analysed. A key and final role in the course will be played by Minsky’s hypothesis on structural financial instability and Mandelbrot’s criticism of standard financial theory.