Book excerpt: Robyn Dawes defines irrationality as adhering to beliefs that are inherently self-contradictory, not just incorrect, self-defeating, or the basis of poor decisions. Such beliefs are unfortunately common. This book demonstrates how such irrationality results from ignoring obvious comparisons, while instead falling into associational and story-based thinking. Strong emotion—or even insanity—is one reason for making automatic associations without comparison, but as the author demonstrates, a lot of everyday judgment, unsupported professional claims, and even social policy is based on the same kind of "everyday" irrationality.