Common Sense, Reasoning, & Rationality is a collection of 11 papers based on some of the invited talks at the Eleventh Vancouver Studies in Cognitive Science conference, held in 1998. A more accurate title would be Commonsense Reasoning and Rationality, and. indeed, that is the phrase used in the title of the editor's introductory chapter. The nineteen authors, mostly philosophers, along with several psychologists, and a couple of computer scientists, are engaged in a debate about the nature of human commonsense reasoning and the applicability of a normative notion of rationality to the study of human commonsense reasoning. The prime contenders, in this book, for a normative notion of rationality are deductive logic and Bayesian probability.