Hayek and the Great Depression of 1929: Did he really change his mind?

The aim of this research is to establish whether, and if so in what way, Hayek changed his mind about the Great Depression of 1929.The work is divided into two parts. In the first part, I present the early' Hayek of the 1930s. Hayek was the great rival of Keynes. Both explained the Great Depression, applying opposing business cycle theories. For Keynes, the crisis was caused by an excess of saving over investment; for Hayek, on the contrary, by an excess of investment over saving. In the early 1930s, Ropke attempted a synthesis, positing that a recession due to overinvestment can degenerate, as in 1929, into a depression caused by oversaving. Hayek examined and rejected Ropke's theory. In the second part, I present the later' Hayek of the 1970s. After years of silence and solitude, Hayek was unexpectedly awarded the Nobel Memorial Prize in Economics, precisely for the contribution he made in the 1930s to the theory of the business cycle. Hayek returned to his pursuit of the ghost of Keynes, debated with his friend and rival Friedman, re-examined Ropke's special case and, according to Haberler, changed his mind. In my conclusion, I attempt to resolve the dilemma.