Abstract

Human decisions are conditioned by formidable uncertainty. The standard resource for dealing rationally with uncertainty is the mathematical concept of probability. The probability calculus is well-known, but since the numerical demands for applying it cannot usually be met, it is not widely applicable. By contrast, the concept of plausibility is widely applicable, but it is little known. This book relies on a generalized concept of plausibility whose strength is its adaptability. The adaptability is due to a novel form of decision theory that takes plausibilities as inputs. This form of decision theory can be adapted to decisions informed by sharp probabilities and utilities as well as to decisions that must be made without them. The book illustrates its application to problems in argumentation theory, scientific theory choice, risk management, ethics, law, economics, and epistemology.