This essay compares the Great Depression to the Great Recession in light of Barry Eichengreen's new book Hall of Mirrors. Eichengreen discusses these two episodes from a historical, Keynesian perspective, and concludes that policies that increase aggregate demand, such as larger fiscal deficits, would have promoted a much stronger and faster recovery from the Great Recession. I review these episodes from a neoclassical approach, which provides a very different perspective on why recoveries from these episodes were so slow and incomplete. I also argue that supply-side policies, rather than demand-side policies, are more likely to restore prosperity today.