Olivier Blanchard and Lawrence H. Summers say that the global financial crisis has forced economists to rethink their previous assumptions about the central role of the financial system and the failure of economies to stabilize without aggressive policies. They explain the nature of “secular stagnation” gripping advanced economies and focus on policies that must be pursued to increase demand. The comments are from the “Rethinking Macroeconomic Policy Conference” held at PIIE on October 12, 2017.