Moral disagreement and non-moral ignorance


The existence of deep and persistent moral disagreement poses a problem for a defender of moral knowledge. It seems particularly clear that a philosopher who thinks that we know a great many moral truths should explain how human populations have failed to converge on those truths. In this paper, I do two things. First, I show that the problem is more difficult than it is often taken to be, and second, I criticize a popular response, which involves claiming that many false moral beliefs are the product of nonmoral ignorance.

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  1. 1.

    Technically, a realist, qua metaphysician, need not take an epistemological position. However, it is probably no accident that existing moral realists are not skeptics: the view is designed to allow us to vindicate the objective truth of our central moral beliefs, or to allow us to “take morality seriously” (Enoch 2011).

  2. 2.

    For discussion see Brink (1984), Shafer-Landau (1994), Loeb (1998), Audi (2008), Enoch (2009), Fitzpatrick (2014).

  3. 3.

    Michelle Moody-Adams argues against this impression (see Moody-Adams 1997). I won’t address her arguments here, except to say that many of them are irrelevant to the problem of moral disagreement that should concern the realist. Moody-Adams spends a great deal of time emphasizing that cultures are not unified, clearly definable units, but no skeptic who wants to deploy disagreement-based arguments should place any weight on the notion of cultural disagreement. Moral diversity amongst human beings, past and present, is enough to get the argument off the ground.

  4. 4.

    Here, the reader could scarcely do better than to consult histories of the Mongol empire, wherein accounts of socially sanctioned mass murder, torture and ethnic cleansing often seem to be on almost every page (Ratchnevsky 1993).

  5. 5.

    See, for example, Alan Gewirth’s defense of a broadly Kantian theory in Gewirth (1994).

  6. 6.

    This is denied by some philosophers. I’ll discuss them in Sect. 1.6.

  7. 7.

    Some historical agents may be off the hook, but I take it that this is intuitive. Suppose that the earliest human populations shared roughly the same basic moral beliefs; it is intuitive that they would not have to confront the problem of moral disagreement.

  8. 8.

    While this might seem too strong, it’s important to remember that as the realist makes moral truths less accessible, they threaten to debunk their own moral beliefs. That is, even if we grant the realist the right to describe themselves as sincere, unbiased inquirers operating under favorable conditions, they still need to believe that such inquirers are quite likely to arrive at the truth. Otherwise, it’s hard to know how they can place much confidence in the proposition that they have arrived at the truth.

  9. 9.

    By “sincere moral inquiry”, I do not wish to imply anything like rarefied philosophical inquiry, or even consciously conducted rational reflection. Rather, I mean something more like preparedness to respond to reasons, where the inquirer’s emotional and cognitive faculties are attuned to the possibility of newer and better moral evidence.

  10. 10.

    The qualifier “important moral matters” is only meant to capture the idea that we must take our core more beliefs to be about important issues. It seems reasonable to say that the beliefs we most care about are those which we also take to concern deeply important matters.

  11. 11.

    See Enoch (2010), Wedgwood (2010), Setiya (2012).

  12. 12.

    For example:

    Many genuine moral disagreements depend on disagreements over the nonmoral facts (Brink 1989)

    Careful philosophical examination will reveal, I believe, that agreement on nonmoral issues would eliminate almost all disagreement about the sorts of moral issues which arise in ordinary moral practice (Boyd 1988).

    Much moral disagreement stems either from disagreement about what the relevant nonmoral facts are, or is due to some error of instrumental reasoning. Clearing up these errors and getting consensus on non-moral facts would remove a great deal of moral disagreement (Shafer-Landau 2003).

  13. 13.

    As quoted in Brown (1992)

  14. 14.

    Importantly, Livingstone-Smith anticipates and rejects the notion that contemporary people have abandoned this conceptual presupposition, noting that “the idea of a normative hierarchy is still very much alive in our moral psychology… [w]e regard our own kind as having the greatest value, and think of animals as having greater value than plants. We esteem “higher” animals like primates more than “lower” animals like invertebrates… terms like “higher” and “lower,” which roll off the tongue so easily, are hierarchical and ultimately normative notions that are inconsistent with a scientific conception of the biosphere.”.

  15. 15.

    Moreover, as psychologists continue to discover that more and more of our apparently “factual” concepts are heavily moralized—that we are, in Joshua Knobe’s words, “moralizing creatures through and through”—the range of disagreements that an NMI-strategist can even in principle explain might shrink even further (Knobe 2010).

  16. 16.

    Of course, an argument which reflected the actual thinking of cockroach-haters would include a number of further background assumptions about cockroaches: that they serve no useful purpose, that they feel no pain, etc. I omit these details only for the sake of clarity. I thank an anonymous reviewer for encouraging me to be clearer about this.

  17. 17.

    Nor does it even entail that I believe (N2), after all, I might just be saying this because I think that you believe (N2).

  18. 18.

    I use the term “definitively” because the middle cases—where only one disagreeing party has the required sort of belief—introduce complexities that I cannot fully address here. Roughly: NMI hypotheses can explain away those disagreements, but they will not always do so.

  19. 19.

    Indeed, this may be something very near to a definitional truth, since it is hard to know how something could count as a “core” moral belief unless it were deeply entwined with emotional commitment. I believe that there’s nothing morally wrong with spitting on the street, and someone might disagree. But I would not leap to a defense of my view or be particularly troubled by the prospect of dropping it. Plausibly, the reason I would respond differently to a disagreement over the moral status of slavery is that my moral belief is deeply rooted in my emotional and intuitive sensibility.

  20. 20.

    Of course, there are extremely silly views about the deterrence effect of capital punishment which might move us if we held them, for example, the view that a single execution will prevent all future violent crime. But this is not relevant to the present debate, since both pro- and anti-capital punishment advocates reject this empirical claim.

  21. 21.

    Here, I am entirely sympathetic to Karen Jones’ discussion in Jones (2005). She suggests that any coherence-method in ethics must adjust its principles in accordance with the huge amount of information about morality that is being produced by the social, historical and anthropological sciences.

  22. 22.

    Indeed, Haidt himself has despaired at the fact that critics of his theory have neglected its deeply social character (Haidt and Bjorklund 2008).

  23. 23.

    For Brink, such a belief is “well informed… results from good inference patterns… is not distorted by obvious forms of prejudice or self-interest… held with some confidence, and is relatively stable over time.” (Brink 1989, p. 132).

  24. 24.

    I should stress that this is consistent with their rejecting a great deal of contemporary moral opinion. All I want to say is that virtually every existing realist moral philosophy is committed to a set of very basic propositions concerning the fundamental equality of persons. This is our contemporary moral legacy, and it is not shared by a huge number of historical cultures.

  25. 25.

    Skeptical arguments which merely cite the possibility of our being massively mistaken in some domain may be more vulnerable to this reply.

  26. 26.

    For example, Brink’s long discussion (1989) of the “distorting” factors which might explain false moral belief contains no historical or psychological detail.


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The author wishes to thank Robert Joynt, Miquel Miralbes del Pino, and Iain Laidley for a great deal of very valuable discussion.

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Smyth, N. Moral disagreement and non-moral ignorance. Synthese (2019).

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  • Moral disagreement
  • Meta-ethics
  • Moral psychology