Abstract

A non-expert who struggles to make good decisions and who turns to decision theory for help, might be more than a little surprised by what they find. If they read a standard treatment of the subject, they will find that they are assumed to be logically omniscient: they know all the logical facts about the propositions whose truth they have considered. Their beliefs are also assumed to be logically closed: if they believe each of a set of propositions S, then they believe everything that can be deduced from S. Finally, they are assumed to be maximally opinionated—they have assigned precise probabilities and cardinal utilities to each possible state of the world that can be formulated via S. The normative core of standard decision theory consists of some very weak axioms for these probabilities and car-dinal utilities, plus the advice to maximize their expected utility, which is a function of the probabil-ities and cardinal utilities for each possible state of the world given each possible choice that they can make. The non-expert might understandably react by saying that this theory is too idealized to be useful for human beings. It is this criticism that Richard Bradley addresses with patience, rigour, and ardour in this book.