What Matters and How it Matters: A Choice-Theoretic Representation of Moral Theories

This paper is a contribution to decision theory and formal ethics. We present a new “reason-based” approach to the formal representation of moral theories, building on recent decision-theoretic work. We show that any moral theory within a very large class can be represented in terms of two parameters: (i) a specification of which properties of the objects of moral choice matter in any given context, and (ii) a specification of how these properties matter. Reason-based representations provide a very general taxonomy of moral theories, as differences among theories can be attributed to differences in their two key parameters. We can thus formalize several salient distinctions among moral theories, such as between consequentialist and non-consequentialist theories, between universalist and relativist theories, between agent-neutral and agent-relative theories, between monistic and pluralistic theories, between atomistic and holistic theories, and between theories with a teleological structure and those without. Reason-based representations also shed light on an important but under-appreciated phenomenon: the “underdetermination of moral theory by deontic content”. In discussing this phenomenon, we draw on ideas from the philosophy of science, particularly in relation to Quine's empirical underdetermination thesis