In the natural sciences, some checks exist on the prolonged acceptance of nutty ideas, which do not hold up well under experimental and observational tests and cannot readily be shown to give rise to useful working technologies. But in economics and the other social studies, nutty ideas may hang around for centuries. Today, leading presidential candidates and tens of millions of voters in the USA embrace ideas that might have been drawn from a 17th-century book on the theory and practice of mercantilism, and multitudes of politicians and ordinary people espouse notions that Adam Smith, David Ricardo, and others exploded more than two centuries ago. In these realms, nearly everyone simply believes whatever he feels good about believing.
