Hume's Law states that you can't derive an 'ought' from an 'is'. Arthur Prior argues that this purported law is disproved by the following counter-instance: 'Tea-drinking is common in England; therefore either tea-drinking is common in England or all New Zealanders ought to be shot'. Prior's argument rests, however, on a less than fully charitable interpretation of Hume's Law. To see this, we need to recognise that a sentence may be partly ethical (partly an 'ought') without be wholly so. When (...) properly interpreted, Hume's Law may be proven true. (shrink)

Various formally valid counterexamples have been adduced against the Humean dictum that one cannot derive an “ought” from an “is.” There are formal rebuttals—some very sophisticated now (e.g., Charles R. Pigden’s and Gerhard Schurz’s)—to such counterexamples. But what follows is an intuitive and informal argument against them. I maintain that it is better than these sophisticated formal defenses of the Humean dictum and that it also helps us see why it implausible to think that we can be as decisive about (...) the truth or falsity of the dictum as both the formal counterexamples or formal barriers to them purport to be. (shrink)

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)

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.

According to global skepticism, we know nothing. According to local skepticism, we know nothing in some particular area or domain of discourse. Unlike their global counterparts, local skeptics think they can contain our invincible ignorance within limited bounds. I argue that they are mistaken. Local skepticism, particularly the kinds that most often get defended, cannot stay local: if there are domains whose truths we cannot know, then there must be claims outside those domains that we cannot know even if they (...) are true. My argument focuses on one popular form of local skepticism, ethical skepticism, but I believe that the argument generalizes to cover other forms as well. (shrink)

Book Information The Is-Ought Problem: An Investigation in Philosophical Logic. By Gerhard Schurz. Kluwer. Dordrecht. 1997. Pp. x + 332. £92.25.

Frank Snare had a puzzle. He construed Hume as a non-cognitivist, indeed, as the non-cognitivist, the fount and origin of contemporary non-cognitivism. Taking Hume to be a non-cognitivist, Snare devoted a great deal of time and effort to the Motivation Argument, or as he called it, the Influence Argument, which he took to be the chief weapon in Hume.

There have been books written since 1997 both on Hume’s ethics and on metaethics generally which make no mention of Gerhard Schurz’s The Is-Ought Problem. I don’t say that they are ipso facto bad books since they may have merits which make up for this glaring defect. But Schurz’s magnificent The Is-Ought Problem is a major contribution to both logic and metaethics and ethicists who disregard it do so at their intellectual peril.

The formulation and proof of Hume’s Law and several related inference barrier theses.

An argument defending the view that one cannot derive an ought from an is against the usual (suspect) counterexamples.