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.

Are there good arguments from Is to Ought? Toomas Karmo has claimed that there are trivially valid arguments from Is to Ought, but no sound ones. I call into question some key elements of Karmo’s argument for the “logical autonomy of ethics”, and show that attempts to use it as part of an overall case for moral skepticism would be self-defeating.

Since the time of Hume, many philosophers have thought it impossible to deduce an ‘Ought’ from an ‘Is,’ or in general to deduce ‘ethical sentences’ from purely ‘factual sentences.’ This is the thesis of the logical autonomy of ethics. I consider a more recent argument by Toomas Karmo in support of the autonomism, but show its limitations in the context of justification skepticism about ethics.

In the current issue of this journal, Scott Hill critiques some of my work on the “is”-“ought” controversy, the Hume-inspired debate over whether an ethical conclusion can be soundly, or even validly, derived from only non-ethical premises. I’ve argued that it can be; Hill is unconvinced. I reply to Hill’s critique, focusing on four key questions to which he and I give different answers.

Hume seems to claim that there does not exist a valid argument that has all non-ethical sentences as premises and an ethical sentence as its conclusion. Starting with Prior, a number of counterexamples to this claim have been proposed. Unfortunately, all of these proposals are controversial. Even the most plausible have a premise that seems like it might be an ethical sentence or a conclusion that seems like it might be non-ethical. Since it is difficult to tell whether any of (...) these counterexamples are genuine, we need a taxonomy that sorts out ethical sentences from non-ethical ones. We need to know the difference between an ‘Is’ and an ‘Ought’. In the first part of the paper, I establish the need for a taxonomy. I consider some of the most influential ‘Is’–‘Ought’ derivations. These include proposals by Prior and Searle. I argue that each proposal has a premise whose status as ethical or non-ethical is difficult to determine. In the second part of the paper, I consider taxonomies proposed by Karmo and Maitzen. I argue against both taxonomies. I end with the claim that we need a taxonomy of ethical sentences and that none of the current proposals are adequate. (shrink)

Toomas Karmo claims that his taxonomy of ethical sentences has the result that there does not exist a sound argument with all non-ethical premises and an ethical conclusion. In a recent paper, Mark T. Nelson argues against this claim. Nelson presents a sound argument that he takes to be such that (i) Karmo’s taxonomy classifies that argument’s single premise as non-ethical and (ii) Karmo’s taxonomy classifies that argument’s conclusion as ethical. I attempt to show that Nelson is mistaken about (ii). (...) For any possible world at which the premise of Nelson’s argument is true, Karmo’s taxonomy classifies the conclusion of Nelson’s argument as non-ethical. (shrink)

The main guiding assumption of this paper is that there is need for a taxonomy of ethical sentences that does not overgenerate, yet can make useful contributions to debates about certain controversial sentences . After surveying the recent literature and concluding that no extant taxonomy that satisfies both of these conditions is available to us, I propose and explain a novel taxonomy which does satisfy them. I then defend my proposal from five potential objections.

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)