Abstract

Psychological experirnents have repeatedly shown that in judging the likelihood of uncertain events people do not follow the principles of probability theory. A notorious example is given by the so called conjunction fallacy. In this paper I argue that this fallacy is not really a fallacy when it is analysed in the light of a dynamic theory of default reasoning. The question that immediately rises is whether the fact that this theory conforms better to the way people actually think provides a reason to prefer it to probability theory.