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Disagreement, Anti-Realism about Reasons, and Inference to the Best Explanation


I defend an inference to the best explanation (IBE) argument for anti-realism about reasons for acting based on the history of intractable disagreement in moral philosophy. The four key premises of the argument are: 1. If there were objective reasons for action, epistemically-well-situated observers would eventually converge upon them after two thousand years; 2. Contemporary philosophers, as the beneficiaries of two thousand years of philosophy, are epistemically well-situated observers; 3. Contemporary philosophers have not converged upon reasons for action; 4. Conclusion: there are no objective reasons for action (IBE from the first three premises). The key premises of the IBE are (1) sentimentalism; (2) non-cognitivism about basic affects; and (3) philosophical arguments for what our reasons for action are always involve arguments that depend on a basic intuitive moral judgment (that can be explained in terms of a basic non-cognitive affect). All these premises are explored in detail, and various objections addressed.

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  1. A threshold objection to this strategy of argument deserves brief consideration. Enoch (2009: 23) notes that “[n]ot every phenomenon calls for explanation—we are inclined to take some facts as brute.” That seems right, but is disagreement a “brute fact” that does not “call” for explanation? Enoch notes that a “full answer…would have to determine first what makes a phenomenon explanatorily interesting,” and confesses, “I know of no satisfactory answer to this question” (2009: 23). We do not need, of course, a full answer to that question, just an answer to the question whether intractable disagreements should be treated as “brute.” Enoch admits that “declaring all cases of moral disagreement as explanatorily uninteresting is a rather desperate (and dogmatic) move” (2009: 23).

    Let us distinguish between the metaphysical claim that some facts are brute, i.e., that they do not admit of further explanation, and the epistemological or practical claim that a phenomenon does not “call” for or warrant an explanation. Many phenomena are brute in the latter sense, but not in the former: e.g., that my bread toasts in the toaster each morning, that the car starts when I turn it on, that my daughter Celia is a terrific cook. None of these phenomena are metaphysically brute, of course, and they all can be explained, but except in unusual circumstances we have no reason, epistemic or practical, to seek out such an explanation: they do not “call for” explanation. Metaphysically brute facts simply do not admit of any further explanation. There may not be many such facts, though this will likely depend on one’s metaphysics. That we experience time as moving forward not backwards, that fundamental physics gives us the best account of matter in motion, that death awaits all living organisms, may all be metaphysically brute facts. The phenomenon of disagreement is obviously not metaphysically brute in any similar sense.

    So Enoch’s challenge should be understood as the demand that we need to articulate when, for epistemic or practical reasons, we should seek an explanation of a phenomenon. We do not, as noted, need a general account of “what makes a phenomenon explanatorily interesting,” since it will suffice if we can identify some features that make a phenomenon explanatorily interesting, and show that disagreement has those features.

  2. An “objective fact” is a mind-independent fact in the following sense: its existence and character does not depend on the epistemic states of other persons, even under epistemically ideal conditions.

  3. Derek Parfit and Joseph Raz seem to be most responsible for this way of talking.

  4. See Leiter (2001) for an overview..

  5. To preempt confusion: I think disagreement among philosophers is more like the birthday cake example than the missing ball example. The latter was meant only to motivate the thought that an explanation was “called” for.

  6. Philosophers—i.e., employed teachers of philosophy in universities—do largely agree about trivial applied propositions that no one has ever disputed, e.g., “No one has a reason to torture babies for fun.” (As an aside, it’s not clear that certain kinds of internalists about reasons, like Sharon Street, do agree with this, but put that worry to one side.) Convergence on applied claims about reasons for action typically belies deeper disagreements about why, say, torturing babies for fun is wrong. (Even where the applied judgments are just brute, the fact of convergence on them admits of other explanations that do not require realism about the matters agreed upon: see the discussion about whether causing suffering is wrong, below.) Philosophers also like to claim, without evidence, that the “folk” generally agree that we should honor agreements, promote the good, and not harm others. But such armchair assertions about what the folk believe are belied by several considerations. What the “folk” actually do is inconsistent with these alleged agreed-upon reasons for acting, which raises a question about whether the folk really accept these reasons. Even worse, the folk are fairly explicit about the ceteris paribus conditions that attach to these reasons: e.g., “do not harm others, unless they deserve it” or “honor agreements, unless the other party is an asshole,” or “iti s wrong, other things being equal, to cause severe suffering to an innocent.” Is there agreement, among the folk even, about who deserves harm, or who the assholes are? I am not aware of any evidence in support of such armchair fantasies. Philosophers affirm from the armchair folk agreement that does not exist in reality. Of course, as soon as we move to the level of philosophical grounds for the particular reasons, the disagreement becomes even more apparent. And philosophers replicate the same problem: e.g., many philosophers might affirm that ‘it is wrong, other things equal, to cause severe suffering to an innocent being,” but everything turns on what “other things equal” means, and here again philosophers differ. Often, in the literature, agreement about “pro tanto” reasons or “pro tanto” wrongness operates the same way: it obscures the real disagreement by bracketing it.

  7. Partfit’s chapter on Nietzsche is not good, but as a matter of academic sociology, those of us in the boring Anglophone world interested in Nietzsche can only be grateful that he thought it worth the bother.  He sent me an early version, and I sent him comments, but it did not salvage the published version.  For criticisms, see Janaway (2017).  

  8. See, e.g., Schroeder (2011).

  9. This is a version of option #4 in Enoch (2009: 21-29); I’ll have more to say about some of his objections in the text.

  10. Someone could deny this, of course, but far less than 2000 years has sufficed for massive progress and convergence in most other cognitive domains. Cf. the discussion of the supposed “youth” of moral philosophy, below.

  11. Cf. Tersman (2006: Ch. 4) discussing arguments in Wright (1992).

  12. Rowland (2017) offers one argument why there cannot be such practical truths. Arguably Nietzsche does too with his quip about Kant: “how could something unknown obligate us?” (Twilight of the Idols). My argument can proceed without defending either of theirs.

  13. Richard Rowland suggests to me that such an argument would parallel that for thinking there are historical truths we cannot know because, e.g., they depend on evidence unavailable to us. But this case is crucially different from the disagreement about reasons-for-acting case: in the former, but not the latter, we know exactly what kind of evidence would settle matters, we just do not, in fact, have access to it. (This is often true in the natural sciences, especially physics.) In the latter case, we don’t even know what the relevant evidence would be, precisely because, as the anti-realist would say, there is no fact of the matter!

  14. I agree with Enoch (2009) and many others (e.g., Brink 1989) that some moral disagreements really mask empirical disagreements, but I do not see that as being at issue in the case I am interested in, i.e., intractable disagreement among moral philosophers. Benthamites and Kantians disagree, but they are not disagreeing about any empirical facts.

  15. Plato, of course, thought that moral (e.g., justice-based) reasons for acting were actually in the agent’s interest, but that is so far from obvious that it demands the famous dialectical efforts of Plato to try to render it plausible.

  16. More precisely, “affect supplies the primary motivation to regard harm as bad. Once this primary motivation is supplied, reasoning proceeds in a currency-like manner [“currency emotions are designed to participate in the process of practical reasoning”]” (Cushman et al. 2010: 63). “[A]larm-bell emotions are designed to circumvent reasoning” (id. at 62) and, arguably, this is “the origin of the welfare principle,” namely “in “Parkinson disease appears to show that intrinstic desires are necessary to the production of motivation in normal human beings, and this would seem to put serious pressure on the cognitivist position” (93)

  17. Note that sentimentalism could be true and well-supported by empirical evidence, but that could be compatible with moral realism.

  18. Views according to which emotions are like perceptions of evaluative properties (e.g., Tappolet 2016) have responses to these sorts of worries, but face many different problems: for one thing, they have to presuppose exactly one of the points in dispute here, namely, whether there are evaluative properties there to be perceived. Some other problems (pertaining to the way in which the analogy between emotional responses and perception breaks down) are usefully reviewed in De Mesel (2017).

  19. Someone might worry that it is not at all “conservative,” but radically revisionary of ordinary “folk” beliefs, to tell people that there is (as Nethanel Lipshitz aptly put it to me) “no such thing as good and evil,” and that there is nothing they objectively have a reason to do or not do. But this kind of worry involves a misunderstanding of conservativism as a demand on choosing better and worse explanations. We should be conservative with our explanations vis-à-vis well-confirmed theories and beliefs about the world, not about folk beliefs and intuitions, which are (outside, say, judgments about midsize physical objects) a notorious hodgepodge of falsehood, delusion and wish-fulfillments.

  20. Max Etchemendy points out to me that there is another IBE in the offing here, which accepts my first three premises, but adds one more, namely, that basic affective responses are not amenable to change through argumentation in seminar rooms or in the pages of philosophy journals. That, too, would explain the failure of convergence among contemporary philosophers, but without taking a position on realism vs. anti-realism about reasons. It would, of course, entail that moral philosophy is irrelevant, and so, in that regard, is a version of the first realist rejoinder considered earlier, i.e., affirming that the truth about reasons for acting transcends what we can know about them. But that raises the question why we should think that is the explanation for the failure of convergence.

  21. The realist may here object that a key difference is that while adult observers will agree that the children are wrongly disputing mere matters of taste in the cake case, they will not so view their moral disagreements. Assuming that is true (the evidence is mixed—consider the economists’ talk of “preferences,” which is ubiquitous in the neoclassical tradition), that simply raises the question what best explains such a meta- view about the status of moral disagreements. It is not clear to me the explanation is really that different in either case, though the habit of academic philosophers of talking only to each other perhaps encourages a different judgment.

  22. A Kantian might think this follows from a more fundamental principle about the dignity of persons, while a utilitarian might take this as a brute starting point, or as following from some principle of utility defended on other grounds.

  23. I use“socialization” very loosely to capture all those psycho-social facts about persons that explain their moral judgments per the IBE sketched earlier.

  24. Someone might object that even those committed to the view that suffering is bad and that inflicting suffering is wrong can allow that those are defeasible normative considerations, and so in fact the Homeric hero is not disagreeing. That could be true if there were evidence that the Homeric hero’s “practical reasoning” worked this way: but, first, Homeric heroes don’t engage in much practical reasoning (at least not as Homer presents them), and second, there is no indication that Homeric heroes are committed to the wrongness of suffering being a normative consideration that needs to be defeated.

  25. Commitment to logical consistency is also an affective commitment, not that widely shared it seems give the history of the world.

  26. I put to one side Aristotle and the neo-Aristotelians with their fanciful assumptions about what it means to be human: they have the distinct advantage of not regarding empirical evidence from the natural and human sciences of what humans are actually like as having any bearing on their ideas.

  27. As noted, above supra n. 17, I do not think Odysseus actually engages in “practical reasoning,” rather than acting instinctively. But this is a separate debate: for skepticism about practical reason, see my discussion of Nietzsche’s view in Leiter (2019), Chapter 5.

  28. Leiter (2001) argues at length that the ontological complexity produces no explanatory payoffs and so fails by IBE standards: I there criticize in details proposals by Brink, J. Cohen, and Sayre-McCord, among others.

  29. Enoch (2009: 27) mischaracterizes the issue when he says (correctly) that “[c]ompeting explanations are evaluated holistically and against a background of prior beliefs,” but then says (falsely) that competing explanations of moral disagreement will “depend on whether we were metaethical realists to being with.” But holistic forms of justification, informed by conservativism, do not assume that just any “prior beliefs” count: it is the “prior beliefs” that we already have good IBE reasons to think are true (i.e., those that are already part of a well-confirmed theory of the world)! But our prior beliefs about realism about reasons for action are precisely what is at issue in the IBE argument, so we cannot presuppose such beliefs in evaluating competing explanations.

  30. The one partial exception is Parfit’s last work, though the extent to which it really engages the competing views is open for some doubt: cf. Schroeder (2011).

  31. It is natural to worry that the problem of intractable disagreement is not limited just to moral philosophy: is not the same the apparently intractable disagreement mirrored in many other parts of our discipline? Are not metaphysicians and epistemologists also not locked in intractable disagreements of their own? Think of debates between internalists and externalists in epistemology, or between presentists and four-dimensionalists in the philosophy of time. If disagreement among moral philosophers supports an abductive inference to denying the existence of moral facts, what, if anything, blocks that inference in all these other cases? Some writers think this kind of “companions in guilt” consideration counts in favor of moral realism, notwithstanding the disagreement among moral philosophers. It is not entirely clear why they rule out, however, the other natural conclusion. Of course, we would need to think carefully about individual cases of philosophical disagreement, since not all of them, in all branches of philosophy, are as intractable or as foundational as they are in moral philosophy. Some philosophical disagreements can, in fact, be defused fairly easily. Thus, to take an example from one of my other fields, the debate in legal philosophy between natural law theorists and legal positivists about the nature of law has both an element of tractability (natural law theorists like John Finnis have, in fact, conceded most of the claims that actually matter to legal positivism) and admits, in the intractable parts, of defusing by reference to the obvious religious commitments of natural law theorists on the remaining issues they refuse to cede. In sum, the skeptical argument from disagreement among philosophers may have implications beyond moral philosophy, but what precisely they are will have to be decided on a case-by-case basis. For discussion, see Leiter (2014).

  32. Alastair Norcross suggests to me that the real problem is that ethics requires reliance on “intuitions,” and our intuitions are still strongly tainted by our religious traditions. That seems a more plausible point, though it is unclear what criteria we are going to appeal to in order to sort the “tainted” from “untainted” intuitions. As Nietzsche would be the first to point out, the utilitarian obsession with sentience and suffering is, itself, indebted to Christianity—an ironic fact, given the centrality of the wrongness of suffering to Parfit’s own moral philosophy (e.g., 2011b, pp. 565 ff.).

  33. I received helpful comments on a very early draft of this paper from Thomas Adams, Max Etchemendy, and Nethanel Lipshitz. A later version benefitted from comments by participants at the Australian Catholic University conference in Rome in September 2018 on “Moral Disagreements.” I should acknowledge, in particular, David Enoch, Don Loeb, Richard Rowland and Folke Tersman. I also received excellent comments on that version from Paul Boswell, University of Chicago Law School Class of 2021. A later version benefitted from discussion with philosophers at the University of Vermont, especially Sin-yee Chan, Tyler Curtain, and, once again, Don Loeb. Finally, I am grateful to two referees for this journal for their comments


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Leiter, B. Disagreement, Anti-Realism about Reasons, and Inference to the Best Explanation. Ethic Theory Moral Prac (2021).

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  • Disagreement
  • Inference to the best explanation
  • Anti-realism
  • Sentimentalism
  • Noncognitivism about affects