Thought: A Journal of Philosophy, EarlyView.

The appealing principle that you can't get an ‘ought’ from an ‘is’, sometimes called Hume's Guillotine , faces a well-known challenge: it must give a clear account of the distinction between normative and descriptive sentences while dodging counter-examples. I argue in this paper that recent efforts to answer this challenge fail because the distinction between normative and descriptive sentences cannot be described well enough to be of any help. As a result, no version of the principle is both true and (...) adequate. Yet a different principle—that no normative terms are synonymous with any descriptive terms—can satisfy much of the motivation we had for defending Hume's Guillotine in the first place. I show briefly how this second principle can explain why is-ought arguments are invalid, block some attempted deductive justifications of beliefs with normative terms, and create an explanatory advantage for moral non-cognitivism. Just so, giving up Hume's Guillotine is the prudent thi.. (shrink)

The ‘No Ought From Is’ principle (or ‘NOFI’) states that a valid argument cannot have both an ethical conclusion and non-ethical premises. Arthur Prior proposed several well-known counterexamples, including the following: Tea-drinking is common in England; therefore, either tea-drinking is common in England or all New Zealanders ought to be shot. My aim in this paper is to defend NOFI against Prior’s counterexamples. I propose two novel interpretations of NOFI and prove that both are true.

Many take the claim that you cannot ‘get’ an ‘ought’ from an ‘is’ to imply that non- moral beliefs are by themselves incapable of justifying moral beliefs. I argue that this is a mistake and that the position that moral beliefs are justified exclusively by non-moral beliefs—a view that I call moral inferentialism—presents an attractive non-sceptical moral epistemology.

This paper investigates, formulates and proves an indexical barrier theorem, according to which sets of non-indexical sentences do not entail (except under specified special circumstances) indexical sentences. It surveys the usual difficulties for this kind of project, as well some that are specific to the case of indexicals, and adapts the strategy of Restall and Russell's "Barriers to Implication" to overcome these. At the end of the paper a reverse barrier theorem is also proved, according to which an indexical sentence (...) will not, except under specified circumstances, entail a non-indexical one. (shrink)

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.

My first paper on the Is/Ought issue. The young Arthur Prior endorsed the Autonomy of Ethics, in the form of Hume’s No-Ought-From-Is (NOFI) but the later Prior developed a seemingly devastating counter-argument. I defend Prior's earlier logical thesis (albeit in a modified form) against his later self. However it is important to distinguish between three versions of the Autonomy of Ethics: Ontological, Semantic and Ontological. Ontological Autonomy is the thesis that moral judgments, to be true, must answer to a realm (...) of sui generis non-natural PROPERTIES. Semantic autonomy insists on a realm of sui generis non-natural PREDICATES which do not mean the same as any natural counterparts. Logical Autonomy maintains that moral conclusions cannot be derived from non-moral premises.-moral premises with the aid of logic alone. Logical Autonomy does not entail Semantic Autonomy and Semantic Autonomy does not entail Ontological Autonomy. But, given some plausible assumptions Ontological Autonomy entails Semantic Autonomy and given the conservativeness of logic – the idea that in a valid argument you don’t get out what you haven’t put in – Semantic Autonomy entails Logical Autonomy. So if Logical Autonomy is false – as Prior appears to prove – then Semantic and Ontological Autonomy would appear to be false too! I develop a version of Logical Autonomy (or NOFI) and vindicate it against Prior’s counterexamples, which are also counterexamples to the conservativeness of logic as traditionally conceived. The key concept here is an idea derived in part from Quine - that of INFERENCE-RELATIVE VACUITY. I prove that you cannot derive conclusions in which the moral terms appear non-vacuously from premises from which they are absent. But this is because you cannot derive conclusions in which ANY (non-logical) terms appear non-vacuously from premises from which they are absent Thus NOFI or Logical Autonomy comes out as an instance of the conservativeness of logic. This means that the reverse entailment that I have suggested turns out to be a mistake. The falsehood of Logical Autonomy would not entail either the falsehood Semantic Autonomy or the falsehood of Ontological Autonomy, since Semantic Autonomy only entails Logical Autonomy with the aid of the conservativeness of logic of which Logical Autonomy is simply an instance. Thus NOFI or Logical Autonomy is vindicated, but it turns out to be a less world-shattering thesis than some have supposed. It provides no support for either non-cognitivism or non-naturalism. (shrink)

This paper is an attempt to apply the truthmaker approach, recently developed by a number of authors, to the problem of providing an adequate formulation of the is–ought gap. I begin by setting up the problem and criticizing some other accounts of how the problem should be stated; I then introduce the basic apparatus of truth-making and show how it may be extended to include both descriptive and normative truth-makers; I next consider how the gap principle should be formulated, attempting (...) to deal as systematically as possible with the ‘harmless’ counter-examples; I also consider the relationship between the gap principle and various other doctrines concerning the separation between the normative and descriptive realms; and I conclude this part of the paper with some general remarks in favor of adopting the truth-maker approach over some of the alternative approaches. The paper concludes with a formal appendix, which gives precise expression to some of claims made in the previous informal part of the paper. (shrink)

I develop and defend metaethical experientialism, the thesis that phenomenal facts explain certain kinds of value facts. I argue, for example, that anyone who knows what it’s like to feel extreme pain is in a position to know that that kind of experience is bad. I argue that metaethical experientialism yields genuine counterexamples to the principle that no ethical conclusion can be derived from purely descriptive premises. I also discuss the prospects for a pluralistic metaethics, whereby different metaethical theories hold (...) for different classes of ethical facts. (shrink)

I was quite excited when I first read Restall and Russell’s (2010) paper. For two reasons. First, because the paper provides rigorous formulations and formal proofs of implication barrier the- ses, namely “theses [which] deny that one can derive sentences of one type from sentences of another”. Second (and primarily), because the paper proves a general theorem, the Barrier Con- struction Theorem, which unifies implication barrier theses concerning four topics: generality, necessity, time, and normativity. After thinking about the paper, I (...) am satisfied with its treatment of the first three topics, namely generality, necessity, and time. But I am not satisfied with its treatment of normativity, so my comments are exclusively on that topic. (shrink)