This chapter examines the impact of the Great Depression on classical economic ideas. When the Great Depression struck after the stock market crash of October 1929, economists in the classical tradition such as Joseph Schumpeter and Lionel Robbins chose to do nothing. They argued that the depression must be allowed to run its course. The chapter first considers U.S. economic policy under Franklin D. Roosevelt, focusing on how he addressed three visible features of the depression: deflation in prices, unemployment, and the hardship depression suffered by especially vulnerable groups. It also discusses the views of two scholars who belonged to the group known as the Roosevelt Brains Trust (later the Brain Trust), Rexford Guy Tugwell and Adolf A. Berle Jr. Finally, it explores how depression and price deflation led to two efforts to raise prices, one through the National Recovery Act and the other through agriculture.