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. Witness two examples: the belief that child sexual abuse can be diagnosed by observing symptoms typically resulting from such abuse, rather than symptoms that differentiate between abused and non-abused children; and the belief that a physical or personal disaster can be understood by studying it alone in-depth rather than by comparing the situation in which it occurred to similar situations where nothing bad happened. This book first demonstrates how such irrationality results from ignoring obvious comparisons. Such neglect is traced to associational and story-based thinking, while true rational judgment requires comparative 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 irrationality.