As readers of this journal can attest to, although philosophers and economists are somewhat used to talking to and learning from each other, it tends to be the subset of philosophers working in decision theory, philosophy of science, and particular areas of ethics and political philosophy that contribute to our interdisciplinary field of research. The book that is the subject of this review symposium, Anna Mahtani’s The Objects of Credence (Oxford University Press, 2024), is a wonderful exemplar of what can be learned when a different branch of philosophy is brought to bear on central questions in this field. Both philosophers and economists talk about and work with credences, or degrees of belief, all the time. These are usually modelled as probabilities, which are in turn usually thought of as attaching to propositions. But it has long been argued by philosophers of language that propositions cannot be the objects of credence. Mahtani’s book is an investigation into all that begins to unravel once we accept this insight. The results have profound implications both for rational choice modelling and for welfare economics.
Coming to decision theory, formal epistemology and philosophy of economics as a philosopher of language, Mahtani has written a book that is thoroughly original and incredibly rich, in the best possible sense. Her opening précis for this symposium not only masterfully summarizes these riches, it also illustrates the exceptional clarity of her writing. What follows are commentaries by Richard Bradley, Luc Bovens, Melissa Fusco and Christian List, based on a book symposium held on 22 May 2023 at Senate House in London. They critically discuss the book’s proposed refinements and revisions to rationality principles such as Reflection, the Principal Principle and – probably of most interest to economists – Ex Ante Pareto; they argue for alternative solutions to the book’s central puzzles; and they propose frameworks for the formal modelling of credences taking on board the book’s key message. The symposium concludes with a response by the author.