This paper argues that decision theory presupposes free will. Although decision theorists seldom acknowledge this, the way decision theory represents, explains, or rationalises choice behaviour acquires its intended interpretation only under the assumption that decision-makers are agents capable of making free choices between alternative possibilities. 

Without that assumption, both normative and descriptive decision theory, including the revealed-preference paradigm, would have to be reinterpreted in implausible ways. The hypothesis that decision-makers have free will is therefore explanatorily indispensable for decision theory. If we regard explanatory indispensability as an indicator of reality in science, decision theorists should embrace the idea of free will. 

Christian List is Professor of Philosophy and Decision Theory and Co-Director of the Munich Center for Mathematical Philosophy at LMU Munich. He works at the intersection of philosophy, economics, and political science, with a particular focus on individual and collective decision-making and the nature of intentional agency. A growing part of his work also addresses metaphysical questions, e.g., about free will, causation, probability, and the relationship between “micro” and “macro” levels of analysis in the human and social sciences.