In the last few decades the accepted opinion among most economists was that the profession understood what caused the Great Depression sufficiently so that we could be confident that we know how to avoid another Great Depression in the future.
Now the accepted opinion is becoming less accepted. I quote below the last sentence of Harold Cole’s review of a 2007 book that surveys current views of the Great Depression by distinguished economists:
(p. 418) I came away from the book struck by the fragmentary state of the science with respect to the Great Depression and the challenges that we still face in terms of developing a truly satisfactory quantitative theory of what happened.
Cole, Harold. “Review of Parker’s “the Economics of the Great Depression”.” Journal of Economic Literature 46, no. 2 (June 2008): 415-18.
The book under review is:
Parker, Randall E. The Economics of the Great Depression: A Twenty-First Century Look Back at the Economics of the Interwar Era. Cheltenham, U.K. and Northampton, Mass.: Elgar, 2007.