"The very term confidence—implying behavior that goes beyond a rational approach to decision making—indicates why it plays a major role in macroeconomics. When people are confident they go out and buy; when they are unconfident they withdraw, and they sell. Economic history is full of such cycles of confidence followed by withdrawal. Who has not taken a hike and come across a long-abandoned railway line— someone’s past dream of a path to riches and wealth? Who has not heard of the Great Tulip Bubble of the seventeenth-century Netherlands— a country famous, we might add, for its stalwart Rembrandt burghers and often caricatured as the home of the world’s most cautious people. Who does not know that even Isaac Newton—the father of modern physics and of the calculus—lost a fortune in the South Sea bubble of the eighteenth century?"