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.

Hume’s Law that one cannot derive an “ought” from an “is” has often been deemed to bear a significance that extends far beyond logic. Repeatedly, it has been invoked as posing a serious threat to views about normativity: naturalism in metaethics and positivism in jurisprudence. Yet in recent years, a puzzling asymmetry has emerged: while the view that Hume’s Law threatens naturalism has largely been abandoned (due mostly to Pigden’s work, see e.g. Pigden 1989), the thought that Hume’s Law is (...) a serious challenge to positivism has only grown in prominence. Our main aim is to establish that Hume’s Law is not a threat to positivism or naturalism. First, we connect extensive, but unfortunately siloed, discussions of this issue. Second, we show that Hume’s Law is not a serious threat to naturalism or positivism, for the gap between logic and such theses is very hard to bridge in a way that would make Hume’s Law able to bear this significance. Finally, we emphasize an implication of our discussion: it undermines one of the main “dialectical tributaries” in jurisprudence (Toh 2018). (shrink)

In this paper, I argue for an interpretation of Hume's Law that sees him as dismissing all possible arguments from is to ought on the basis of a comparison with his famous argument on induction.

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)

It is regrettably common for theorists to attempt to characterize the Humean dictum that one can’t get an ‘ought’ from an ‘is’ just in broadly logical terms. We here address an important new class of such approaches which appeal to model-theoretic machinery. Our complaint about these recent attempts is that they interfere with substantive debates about the nature of the ethical. This problem, developed in detail for Daniel Singer’s and Gillian Russell and Greg Restall’s accounts of Hume’s dictum, is of (...) a general type arising for the use of model-theoretic structures in cashing out substantive philosophical claims: the question of whether an abstract model-theoretic structure successfully interprets something often involves taking a stand on non-trivial issues surrounding the thing. In the particular case of Hume’s dictum, given reasonable conceptual or metaphysical claims about the ethical, Singer’s and Russell and Restall’s accounts treat obviously ethical claims as descriptive and vice versa. Consequently, their model-theoretic characterizations of Hume’s dictum are not metaethically neutral. This encourages skepticism about whether model-theoretic machinery suffices to provide an illuminating distinction between the ethical and the descriptive. (shrink)

Some philosophers think that there is a gap between is and ought which necessarily makes normative enquiry a different kind of thing than empirical science. This position gains support from our ability to explicate our inferential practices in a way that makes it impermissible to move from descriptive premises to a normative conclusion. But we can also explicate them in a way that allows such moves. So there is no categorical answer as to whether there is or is not a (...) gap. The question of an is-ought gap is a practical and strategic matter rather than a logical one, and it may properly be answered in different ways for different questions or at different times. (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.

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)

I argue that Colin Cheyne and Charles Pigden's recent attempt to find truthmakers for negative truths fails. Though Cheyne and Pigden are correct in their treatment of some of the truths they set out to find truthmakers for (such as 'There is no hippopotamus in S223' and 'Theatetus is not flying') they over-generalize when they apply the same treatment to 'There are no unicorns'. In my view, this difficulty is ineliminable: not every truth has a truthmaker.

Priority Theory is an increasingly popular view in metaphysics. By seeing metaphysical questions as primarily concerned with what explains what, instead of merely what exists, it promises not only an interesting approach to traditional metaphysical issues but also the resolution of some outstanding disputes. In a recent paper, Louis deRosset argues that Priority Theory isn’t up to the task: Priority Theory is committed to there being explanations that violate a formal constraint on any adequate explanation. This paper critically examines deRosset’s (...) challenge to Priority Theory. We argue that deRosset’s challenge ultimately fails: his proposed constraint on explanation is neither well-motivated nor a general constraint. Nonetheless, lurking behind his criticism is a deep problem for prominent ways of developing Priority Theory, a problem which we develop. (shrink)

In “Why We Need Friendly AI”, Luke Muehlhauser and Nick Bostrom propose that for our species to survive the impending rise of superintelligent AIs, we need to ensure that they would be human-friendly. This discussion note offers a more natural but bleaker outlook: that in the end, if these AIs do arise, they won’t be that friendly.

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 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 construct “remembering” is equivocal between an epistemic sense, denoting a distinctive ground for knowledge, and empirical sense, denoting the typical behavior of a neurocognitive mechanism. Because the same kind of equivocation arises for other psychologistic terms (such as believe, decide, know, judge, decide, infer and reason), the effort to spot and remedy the confusion in the case of remembering might prove generally instructive. The failure to allow these two senses of remembering equal play in their respective domains leads, I (...) argue, to unnecessary confusion about memory externalism, the possibility of episodic memory in non-human species, and the thesis of memory continuism. By distinguishing these equivocal senses of remembering, we thus gain leverage on understanding how the distinctive epistemic norms that define many of our psychologic terms are more plausibly related to the capacities studied by empirical science, given that neither identity nor elimination are possible. (shrink)

It was something of a dogma for much of the twentieth century that one cannot validly derive an ought from an is. More generally, it was held that non-normative propositions do not entail normative propositions. Call this thesis about the relation between the natural and the normative Natural-Normative Autonomy. The denial of Autonomy involves the entanglement of the natural with the normative. Naturalism entails entanglement—in fact it entails the most extreme form of entanglement—but entanglement does not entail naturalism. In a (...) ground-breaking paper “The autonomy of ethics” Arthur Prior constructed some intriguing counterexamples to Autonomy. While his counterexamples have convinced few, there is little agreement on what is wrong with them. I present a new analysis of Autonomy, one which is grounded in a general and independently plausible account of subject matters. While Prior’s arguments do establish shallow natural-normative entanglement, this is a consequence of simple logical relationships that hold between just about any two subject matters. It has nothing special to do with the logical structure of normativity or its relation to the natural. Prior’s arguments leave the fundamental idea behind natural-normative Autonomy intact. I offer a new argument for deep entanglement. I show that in any framework adequate for dealing with the natural and the normative spheres, a purely natural proposition entails a purely normative proposition, and vice-versa. But this is no threat to non-naturalist moral realism. In fact it helps ameliorate the excesses of an extreme non-naturalism, delivering a more palatable and plausible position. (shrink)

Moral conclusions cannot validly be inferred from nonmoral premises – this principle, commonly called “Hume’s law,” presents a conundrum. On one hand, it seems obviously true, and its truth is often simply taken for granted. On the other hand, an ingenious argument by A. N. Prior seems to refute it. My aim here is a resolution. I shall argue, first, that Hume’s law is ambiguous, admitting both a strong and a weak interpretation; second, that the strong interpretation is false, as (...) shown by Prior’s argument; and, third, that the weak interpretation is true. (shrink)

The autonomy thesis is the claim that one cannot get a normative statement from purely descriptive statements. But despite its intuitive appeal a precise formulation of the thesis has remained elusive. In a recent paper, Maguire makes the promising suggestion that the thesis should be understood in terms of ground. But Maguire’s formulation, I argue, is based on controversial taxonomic assumptions that make the autonomy thesis into a non-substantive claim. I develop an alternative ground-based formulation of the autonomy thesis that (...) appeals to the notion of normative relevance, which is in turn understood using the tools of truthmaker semantics. This formulation of the autonomy thesis avoids well-known counterexamples to other formulations and has significant advantages over Maguire’s formulation. (shrink)

In “A neglected reply to Prior’s dilemma” Beall [2012] presents a Weak Kleene framework where Prior’s dilemma for Hume’s no-ought-fromis thesis fails. It fails in the framework because addition, the inference rule that one of its horns relies on, is invalid. In this paper, we show that a more general result is necessary for the viability of Beall’s proposal – a result, which implies that Hume’s thesis holds in the proposed framework. We prove this result and thus show that Beall’s (...) proposal is indeed viable. (shrink)

(2013). In the beginning was the doing: the premises of the practical syllogism. Canadian Journal of Philosophy: Vol. 43, No. 3, pp. 303-321.

Token-reflexive theories of indexicals – words like ‘I,’ ‘here,’ and ‘today’ – are widely thought to face a problem in account for intuitively valid arguments involving indexicals. Yet all discussions of the problem with which I am familiar focus on particular examples or on particular rules of inference. In this paper, I first state the problem in its full generality, and then argue that two recent attempts to reject the problem fail. Finally, I consider the proposal by García-Carpintero that demonstratives (...) – ‘this’ and ‘that’ – raise the same problem. I argue that while there are important similarities between the logic problem for token-reflexives and the role of demonstratives in logic, recent work on the logic of demonstratives can offer insights into logic that token-reflexive theories cannot. (shrink)

This article is concerned with the interconnection between three arguments: the Moral Explanatory Dispensability Argument, the Epistemic Explanatory Dispensability Argument, and the Companions in Guilt Argument. Silvan Wittwer has recently argued that the Epistemic EDA is self-effacing, whereas the Moral EDA is not. This difference between them is then leveraged by Wittwer to establish that there is a significant disparity between these arguments and that this disparity undermines attempts to use the CGA as a means of refuting the Moral EDA. (...) After explaining the connections between these arguments, I provide three different responses to Wittwer’s analysis. First, I develop a plausible case in favor of the conclusion that the Moral EDA is also self-effacing. Second, I defend the Epistemic EDA from the charge of self-effacement and respond to Wittwer’s assertion that my preferred method of escaping his argument is dialectically inappropriate. Finally, I explain how some arguments recently articulated by Richard Rowland and Ramon Das support my objections to Wittwer’s self-effacement argument. (shrink)