This paper proves a precisification of Hume’s Law—the thesis that one cannot get an ought from an is—as an instance of a more general theorem which establishes several other philosophically interesting, though less controversial, barriers to logical consequence.

The central question for this dissertation is, how do we do moral philosophy well from within a broadly naturalist framework? Its main goal is to lay the groundwork for a methodological approach to moral philosophy that integrates traditional, intuition-driven approaches to ethics with empirical approaches that employ empirical data from biology and cognitive science. Specifically, it explores what restrictions are placed on our moral theorizing by findings in evolutionary biology, psychology, neuroscience, and other fields, and how we can integrate this (...) data while still offering a fully normative account of ethics. To that end, the dissertation explores the methodological assumptions behind both traditional and more empirical or experimental approaches to ethics, to find where these assumptions cannot be properly supported and need to be re-examined. Chapter 1 explores the science-based objections that have been raised to traditional approaches, with a particular focus on questions concerning the reliability of moral intuitions. Chapter 2 examines three fundamental assumptions supporting the empirical approach to moral philosophy, and how those assumptions ultimately do not fit with how we ought to understand the project of ethics. In chapter 3, I discuss the fact/value distinction, and the restrictions that are placed on our moral theorizing by our commitment to this distinction. Chapter 4 offers a defense of ‘companions in guilt’ arguments, and uses these arguments to draw an analogy between moral philosophy and epistemology that will be used to help defend moral philosophy against empirical debunking arguments. Chapter 5 explores the ways in which epistemologists’ methods of incorporating empirical data into their research while maintaining the normativity of their accounts can be adapted to allow moral philosophers to do the same, and brings together the various methodological concerns addressed up to this point to lay out a methodological approach I call empirically-informed moral philosophy. (shrink)