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The epistemology of evolutionary debunking


Fifteen years ago, Sharon Street and Richard Joyce advanced evolutionary debunking arguments against moral realism, which purported to show that the evolutionary history of our moral beliefs makes moral realism untenable. These arguments have since given rise to a flurry of objections; the epistemic principles Street and Joyce relied upon, in particular, have come in for a number of serious challenges. My goal in this paper is to develop a new account of evolutionary debunking which avoids the pitfalls Street and Joyce encountered and responds to the most pressing objections they faced. I begin by presenting a striking thought experiment to serve as an analogy for the evolution of morality; I then show why calibrationist views of higher-order evidence are crucial to the evolutionary debunking project; I outline a new rationale for why finding out that morality was selected to promote cooperation suggests that our moral judgments are unreliable; and I explain why evolutionary debunking arguments do not depend on our having a dedicated faculty for moral cognition. All things considered, I argue, evolutionary debunking arguments against moral realism are on relatively secure footing – provided, at least, that we accept a calibrationist account of higher-order evidence.

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  1. For comparison, Ayer-style emotivists will reject all four theses, error theorists will reject the third, and moral relativists and constructivists will reject the fourth. There are a few meta-ethical views – I am thinking especially of thin forms of reductive naturalism, like those defended by Copp (2008) and Sterelny and Fraser (2017) – where it is unclear whether we should categorize them as realist or anti-realist. I will not be addressing these sorts of views here.

  2. See Horn (2017) and Lutz (2018) for more recent presentations of evolutionary debunking arguments, and Korman (2019) for a review of the evolutionary debunking literature.

  3. See Sect. 3.5 and the references therein.

  4. Yong (2016) gives a nice popular overview of the evolution of vision.

  5. Some philosophers writing on evolutionary debunking arguments, beginning with Street, contrast the thesis that our moral sense was selected to acquire true beliefs with the thesis that it was selected for survival and reproduction, or the thesis that it was selected to promote fitness. This is a confusion; trivially, all selection favors organisms who are fitter or more successful at surviving and reproducing than their conspecifics, so it makes no sense to say that a trait was selected for survival and reproduction or for fitness. What we are interested in when we inquire what a trait was selected for is which (if any) of its effects boosted our ancestors' reproductive fitness and thereby caused the genes associated with that trait to proliferate throughout our species.

  6. See White (2010), Shafer-Landau (2012), Vavova (2014; forthcoming), Bogardus (2016), Clarke-Doane (2016), Sinclair (2018) and Clarke-Doane and Baras (2021). The most important points of criticism, to my mind, are that Joyce's version of the argument depends on a causal epistemic principle that is widely believed to be false (although see Korman and Locke (2020) for a defense), while the epistemic principle Street invokes is not clearly spelled out but implausible on most interpretations. The argument I develop in this paper replaces these principles with a version of the calibrationist view of higher-order evidence, which enjoys substantial (but by no means universal) support in the literature.

  7. I should note that it seems likely to me that any evolutionary debunking argument is liable to struggle with Moorean responses (Sect. 4.1) and third-factor explanations (Sect. 4.2) unless it avails itself of calibrationism and its associated independence requirement.

  8. I understand the moral sense to be the faculty that generates our gut reactions or intuitions in ethics, both about particular cases (real or hypothetical) and about general principles. For instance, it is the moral sense which intimates to us that torturing children is wrong, that generosity is a virtue, and which makes “maximize the amount of well-being in the world” – but not “maximize the amount of injustice in the world” – seem like a plausible moral principle. I suggest, moreover, that the moral sense plays an indispensable epistemic role in justifying our moral beliefs (inasmuch as they are justified at all); none of our moral beliefs could lay claim to any positive epistemic status if not for the base-level infusion of evidence supplied by the moral sense. Note, though, that nothing in this paper hangs on how I am conceiving of the moral sense. In the end, I will argue that evolutionary debunking arguments succeed even if our brains turn out not to contain any kind of specialized faculty for moral cognition.

  9. See Machery and Mallon (2010), FitzPatrick (2015) and Levy and Levy (2020).

  10. White (2010), for one, defends this view.

  11. Just so the thought experiment is not confounded by ethical concerns, I ask the reader to assume, somewhat implausibly, that the radiation would not have caused harmful congenital disorders in the Transarcturians' offspring, and that their disposition to avoid trespassing in the forbidden zones, if the Earth scientists' hypothesis is correct, is the result of selection operating directly on the Transarcturians' genes. The idea is that any genes which predisposed the Transarcturians to steer clear of the forbidden zones were favored by selection just because those genes were less likely to be altered by the mutagenic effects of the radiation.

  12. Note that the Transarcturians do not believe that the forbidden zones are, in general, dangerous; they see “forbiddenness” as an intrinsic normative feature of certain areas of their world, just as we see goodness as an intrinsic normative feature of certain states of affairs.

  13. Of course, if the Transarcturians could offer an alternative account of the etiology of their forbiddenness faculty suggesting that it was selected to produce true beliefs, and this account was clearly better-supported by the available evidence than the Earth scientists' conjecture, that would change their epistemic situation substantially. But we are assuming they have no such account to offer.

  14. Some externalists about justification may insist that the Transarcturians' forbiddenness beliefs, because they were unreliably formed, were never even prima facie justified and hence cannot be undermined or defeated. Proponents of radically aprioristic moral epistemologies which hold that false moral beliefs can never be justified may be inclined to say the same thing. There are two questions to separate here: the first is whether it makes sense to describe beliefs that are not prima facie justified as being undermined or defeated, while the second concerns how the Earth scientists' discovery should affect the epistemic status of the Transarcturians' beliefs, assuming they were never justified to begin with. The first of these questions strikes me as a semantic matter of limited significance, so I will focus on the latter. Even if we say the Transarcturians' forbiddenness beliefs were unjustified to begin with, there is still a clear sense, I think, in which they held those beliefs rationally, or reasonably, or blamelessly, prior to the revelation about their evolutionary history. It's hard to fault them for trusting intuitions that are built into their minds from birth and widely shared throughout their species. My contention is that, after hearing about the Earth scientists' discovery, intuitively, their forbiddenness beliefs cease being rational, or reasonable, or blameless in this sense, and that this is the sort of change to a belief's epistemic status that would normally defeat its justification, had it been justified in the first place. And, if this subjunctive or counterfactual claim about the Transarcturians' beliefs is true, that's all that will be needed to underwrite the intended analogy between the forbidden zones and morality. Of course, realists have the option of biting the bullet and insisting that hearing about the Earth scientists' discovery should have no effect whatsoever on the epistemic status of the Transarcturians' beliefs. But it seems to me that this still comes at the cost of saying something counter-intuitive about the case.

  15. Compare the formalizations in Shafer-Landau (2012) and Morton (2016).

  16. Note that – as their names indicate – the schematic versions of both the epistemic principle and the etiological principle (Sect. 3.3) are supposed to be true for all substitution instances of their variables. This is not the case for the schematic versions of the autonomy clause (Sect. 3.4) or the empirical premise.

  17. For helpful discussion of higher-order evidence, see Christensen (2010) and DiPaolo (2018).

  18. Sliwa and Horowitz (2015) present a clear and accessible defense of the view. See also White (2009), Christensen (2016), Schoenfield (2018), Vavova (2018) and Kappel (2019), along with Schoenfield (2015) and Isaacs (2021) for criticism. Calibrationism is usually formulated in terms of credences, but for the sake of simplicity, I will stick to all-or-nothing beliefs here.

  19. The independence requirement first emerged from the literature on peer disagreement, and most discussion of it has been restricted to that context. Elga (2007) and Christensen (2007; 2009; 2011; 2018; 2019) defend the requirement, while Arsenault and Irving (2012), Kelly (2013) and Lord (2014) number among its detractors. Vavova (2014) discusses the independence requirement in connection with evolutionary debunking.

  20. Vavova (2018) draws this distinction clearly.

  21. Note, though, that even if a view like Kelly's turns out to be correct, this is not necessarily a fatal blow for the evolutionary debunking project. Calibrationism undoubtedly makes things much easier for the debunker, but the total-evidence view still implies that higher-order evidence of unreliability will often (although not always) serve to defeat the justification for our first-order beliefs.

  22. Although the principle, as presented, concerns natural selection and belief-forming mechanisms, due to the well-known conceptual parallels between functions conferred by selection and functions conferred by design, it can readily be extended to apply to scientific instruments and other information-gathering artifacts as well. I will exploit these parallels in one example later in this section.

  23. Note that this rule is only intended as a statistical generalization, which means that evidence that a belief-forming mechanism was selected to φ has the potential to be screened off – rendered probabilistically irrelevant – by more specific information about the nature of φ-ing and ψ-ing. The rule is important here because of the context created by the independence requirement, where we are bracketing off the outputs of the belief-forming mechanism in question and evaluating its reliability from a position of relative ignorance. This will often leave us without much admissible information about the nature of ψ-ing, allowing facts about the belief-forming mechanism's causal history to take on a larger evidential role. A slightly different type of example will help to illustrate: knowing nothing about pharmacognosy, you should think it unlikely that a piece of tree bark would be effective at curing a headache, because bark is selected to protect the tree's inner layers from the elements, not to produce medically valuable effects in humans. But the evidential significance of this fact about the evolved function of tree bark would be screened off by knowledge that the bark in question comes from the willow tree, and so contains the compound salicin, from which aspirin was derived.

  24. Several authors, including Berker (2014), have wondered whether the success of evolutionary debunking arguments really depends on the finer details of our evolutionary history. The rationale for the etiological principle I have presented here suggests that it does. For the debunking argument to work, it is essential that (to the best of our knowledge) our moral sense was selected for a function other than generating true moral beliefs. Other possible etiologies will not be as congenial to the debunker. For instance, were we to discover that our moral beliefs have never been shaped by selection at all, and are instead the product of a completely domain-neutral information-processing mechanism in the brain, it is not clear that an evolutionary debunking argument targeting moral realism would be viable.

  25. I discuss a related objection, involving so-called third-factor explanations, in Sect. 4.2.

  26. There is a large volume of literature on this topic (see, for instance, Larmore (2008) and McPherson (2008)) that I cannot hope to adequately summarize here. In what follows I will focus on presenting what I take to be the most compelling reason for thinking that the autonomy clause is true of morality.

  27. For a variety of perspectives, see, in addition to Joyce (2006), Alexander (1987), Richerson and Boyd (2005), Hauser (2006), Bowles and Gintis (2011), Kitcher (2011), Baumard et al. (2012), Boehm (2012), Tomasello (2016) and Sterelny (2021).

  28. According to calibrationism, that is. Philosophers who reject calibrationism, or who wish to restrict its scope, may insist that there is a privileged set of beliefs, perhaps including some moral beliefs, which are so obvious or self-evident that they can never be defeated by higher-order evidence.

  29. For compelling criticism of third-factor explanations along different lines than those pursued here, see Lutz (2018). Tersman (2017) and Klenk (2020) discuss third-factor explanations in the context of moral disagreement.

  30. Compare Morton (2016) on this point.

  31. To the best of my knowledge, this view originates with Ruse (1986).


  • Alexander, R. (1987). The Evolution o f Moral Systems. AldineTransaction.

    Google Scholar 

  • Arsenault, M., & Iriving, Z. (2012). Aha! Trick Questions, Independence, and the Epistemology of Disagreement. Thought: A Journal of Philosophy, 1(3), 185–194.

  • Baumard, N., Andre, J., & Sperber, D. (2012). A Mutualistic Approach to Morality: The Evolution of Morality By Partner Choice. Behavioral and Brain Sciences, 36(1), 59–78.

    Google Scholar 

  • Berker, S. (2014). Does Evolutionary Psychology Show That Normativity is Mind-Dependent?. In J. D'Arms & D. Jacobson (Eds.), Moral Psychology and Human Agency: Essays on the New Science of Ethics. Oxford University Press.

  • Boehm, C. (2012). Moral Origins: The Evolution of Virtue, Altruism, and Shame. Basic Books.

    Google Scholar 

  • Bogardus, T. (2016). Only All Naturalists Should Worry About Only One Evolutionary Debunking Argument. Ethics, 126(3), 636–661.

    Google Scholar 

  • Bowles, S., & Gintis, H. (2011). A Cooperative Species: Human Reciprocity and Its Evolution. Princeton University Press.

    Google Scholar 

  • Brosnan, K. (2011). Do the Evolutionary Origins of Our Moral Beliefs Undermine Moral Knowledge? Biology and Philosophy, 26(1), 51–64.

    Google Scholar 

  • Christensen, D. (2007). Epistemology of Disagreement: The Good News. Philosophical Review, 116(2), 187–217.

    Google Scholar 

  • Christensen, D. (2009). Disagreement as Evidence: The Epistemology of Controversy. Philosophy Compass, 4(5), 756–767.

    Google Scholar 

  • Christensen, D. (2010). Higher-Order Evidence. Philosophy and Phenomenological Research, 81(1), 185–215.

    Google Scholar 

  • Christensen, D. (2011). Disagreement, Question-Begging and Epistemic Self-Criticism. Philosophers’ Imprint, 11(6), 1–22.

    Google Scholar 

  • Christensen, D. (2016). Disagreement, Drugs, Etc.: From Accuracy to Akrasia. Episteme, 13(4), 397–422.

    Google Scholar 

  • Christensen, D. (2018). On Acting as Judge in One’s Own Epistemic Case. Proceedings and Addresses of the American Philosophical Association, 93(1), 207–235.

    Google Scholar 

  • Christensen, D. (2019). Formulating Independence. In M. Rasmussen & A. Steglich-Petersen (Eds.), Higher-Order Evidence: New Essays. Oxford University Press.

  • Clarke-Doane, J. (2016). Debunking and Dispensability. In U. Leibowitz & N. Sinclair (Eds.), Explanation in Ethics and Mathematics: Debunking and Dispensability. Oxford University Press.

  • Clarke-Doane, J., & Baras, D. (2021). Modal Security. Philosophy and Phenomenological Research, 102(1), 162–183.

    Google Scholar 

  • Copp, D. (2008). Darwinian Skepticism About Moral Realism. Philosophical Perspectives, 18(1), 186–206.

    Google Scholar 

  • Dennett, D. (1991). Consciousness Explained. Little, Brown and Company.

    Google Scholar 

  • Dennett, D. (2013). Bestiary of the Manifest Image. In D. Ross, J. Ladyman, & H. Kincaid (Eds.), Scientific Metaphysics. Oxford University Press.

  • Dennett, D. (2016). Illusionism As the Obvious Default Theory of Consciousness. Journal of Consciousness Studies, 23(11–12), 65–72.

    Google Scholar 

  • Dennett, D. (2017). From Bacteria to Bach and Back: The Evolution of Minds. W. W. Norton.

    Google Scholar 

  • DiPaolo, J. (2018). Higher-Order Defeat is Object Independent. Pacific Philosophical Quarterly, 99(2), 248–269.

    Google Scholar 

  • Elga, A. (2007). Reflection and Disagreement. Nous, 41(3), 478–502.

    Google Scholar 

  • Enoch, D. (2010). The Epistemological Challenge to Metanormative Realism: How Best to Understand It and How to Cope With It. Philosophical Studies, 148(3), 413–438.

    Google Scholar 

  • FitzPatrick, W. (2015). Debunking Evolutionary Debunking of Moral Realism. Philosophical Studies, 172(4), 883–904.

    Google Scholar 

  • Fuqua, J. (forthcoming). Metaethical Mooreanism and Evolutionary Debunking. Proceedings of the American Catholic Philosophical Association. <>.

  • Gould, S., & Lewontin, R. (1979). The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme. Proceedings of the Royal Society of London, Series b: Biological Sciences, 205(1161), 581–598.

    Google Scholar 

  • Hauser, M. (2006). Moral Minds: The Nature of Right and Wrong. HarperCollins.

    Google Scholar 

  • Horn, J. (2017). Evolution and the Epistemological Challenge to Moral Realism. In M. Ruse & R. Richards (Eds.), The Cambridge Handbook of Evolutionary Ethics. Cambridge University Press.

  • Isaacs, Y. (2021). The Fallacy of Calibrationism. Philosophy and Phenomenological Research, 102(2), 247–260.

    Google Scholar 

  • Joyce, R. (2006). The Evolution of Morality. MIT Press.

    Google Scholar 

  • Joyce, R. (2013). The Evolutionary Debunking of Morality. In J. Feinberg & R. Shafer-Landau (Eds.), Reason and Responsibility. Cengage.

  • Joyce, R. (2016). Evolution, Truth-Tracking, and Moral Skepticism. In Essays in Moral Skepticism. Oxford University Press.

  • Kappel, K. (2019). Escaping the Akratic Trilemma. In M. Skipper & A. Steglich-Petersen (Eds.), Higher-Order Evidence: New Essays. Oxford University Press.

  • Kelly, T. (2010). Peer Disagreement and Higher-Order Evidence. In R. Feldman & T. Warfield (Eds.), Disagreement. Oxford University Press.

  • Kelly, T. (2013). Disagreement and the Burdens of Judgment. In D. Christensen & J. Lackey (Eds.), The Epistemology of Disagreement: New Essays. Oxford University Press.

  • Kitcher, P. (2011). The Ethical Project. Harvard University Press.

    Google Scholar 

  • Klenk, M. (2020). Third Factor Explanations and Disagreement in Metaethics. Synthese, 197(1), 427–446.

    Google Scholar 

  • Korman, D. (2019). Debunking Arguments. Philosophy Compass, 14(12), 1–17.

    Google Scholar 

  • Korman, D., & Locke, D. (2020). Against Minimalist Responses to Moral Debunking Arguments. In R. Shafer-Landau (Ed.), Oxford Studies in Metaethics Volume 15. Oxford University Press.

  • Larmore, C. (2008). The Autonomy of Morality. Cambridge University Press.

    Google Scholar 

  • Levy, A., & Levy, Y. (2020). Evolutionary Debunking Arguments Meet Evolutionary Science. Philosophy and Phenomenological Research, 100(3), 491–509.

    Google Scholar 

  • Lord, E. (2014). From Independence to Conciliationism: An Obituary. Australasian Journal of Philosophy, 92(2), 365–377.

    Google Scholar 

  • Lutz, M. (2018). What Makes Evolution a Defeater? Erkenntnis, 83(6), 1105–1126.

    Google Scholar 

  • Machery, E., & Mallon, R. (2010). Evolution of Morality. In J. Doris (Ed.), The Moral Psychology Handbook. Oxford University Press.

  • McPherson, T. (2008). Metaethics and the Autonomy of Morality. Philosophers’ Imprint, 8(6), 1–16.

    Google Scholar 

  • Morton, J. (2016). A New Evolutionary Debunking Argument Against Moral Realism. Journal of the American Philosophical Association, 2(2), 233–253.

    Google Scholar 

  • Richerson, P., & Boyd, R. (2005). Not By Genes Alone: How Culture Transformed Human Evolution. The University of Chicago Press.

    Google Scholar 

  • Ruse, M. (1986). Evolutionary Ethics: A Phoenix Arisen. Zygon, 21(1), 95–112.

    Google Scholar 

  • Schoenfield, M. (2015). A Dilemma for Calibrationism. Philosophy and Phenomenological Research, 91(2), 425–455.

    Google Scholar 

  • Schoenfield, M. (2018). An Accuracy-Based Approach to Higher-Order Evidence. Philosophy and Phenomenological Research, 96(3), 690–715.

    Google Scholar 

  • Shafer-Landau, R. (2012). Evolutionary Debunking, Moral Realism and Moral Knowledge. Journal of Ethics and Social Philosophy, 7(1), 1–37.

    Google Scholar 

  • Sinclair, N. (2018). Belief Pills and the Possibility of Moral Epistemology. In R. Shafer-Landau (Ed.), Oxford Studies in Metaethics Volume 13. Oxford University Press.

  • Skarsaune, K. (2011). Darwin and Moral Realism: Survival of the Iffiest. Philosophical Studies, 152(2), 229–243.

    Google Scholar 

  • Sliwa, P., & Horowitz, S. (2015). Respecting All the Evidence. Philosophical Studies, 172(11), 2835–2858.

    Google Scholar 

  • Sterelny, K. (2021). The Pleistocene Social Contract: Culture and Cooperation in Human Evolution. Oxford University Press.

    Google Scholar 

  • Sterelny, K., & Fraser, B. (2017). Evolution and Moral Realism. British Journal for the Philosophy of Science, 68(4), 981–1006.

    Google Scholar 

  • Street, S. (2006). A Darwinian Dilemma for Realist Theories of Value. Philosophical Studies, 127(1), 109–166.

    Google Scholar 

  • Street, S. (2015). Does Anything Really Matter or Did We Just Evolve to Think So? In A. Byrne, J. Cohen, G. Rosen, & S. Shiffrin (Eds.), The Norton Introduction to Philosophy. Norton.

  • Tersman, F. (2017). Debunking and Disagreement. Nous, 51(4), 754–774.

    Google Scholar 

  • Tomasello, M. (2016). A Natural History of Human Morality. Harvard University Press.

    Google Scholar 

  • Vavova, K. (2014). Debunking Evolutionary Debunking. In R. Shafer-Landau (Ed.), Oxford Studies in Metaethics Volume 9. Oxford University Press.

  • Vavova, K. (2018). Irrelevant Influences. Philosophy and Phenomenological Research, 96(1), 134–152.

    Google Scholar 

  • Vavova, K. (forthcoming). The Limits of Rational Belief Revision: A Dilemma for the Darwinian Debunker. Nous. <>.

  • Wielenberg, E. (2010). On the Evolutionary Debunking of Morality. Ethics, 120(3), 441–464.

    Google Scholar 

  • White, R. (2009). On Treating Oneself and Others As Thermometers. Episteme, 6(3), 233–250.

    Google Scholar 

  • White, R. (2010). You Just Believe that Because…. Philosophical Perspectives, 24(1), 573–615.

    Google Scholar 

  • Yong, E. (2016). Inside the Eye: Nature's Most Exquisite Creation. National Geographic February 2016 Edition.

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I would like to thank Dallas Amico, Louise Antony, Philip Bricker, David Christensen, Patrick Grafton-Cardwell, Sophie Horowitz, Tim Juvshik, Hilary Kornblith, Christopher Meacham, Keehyuk Nahm, Ryan Olsen, and Alejandro Perez Carballo, along with several anonymous referees, for their helpful comments on previous drafts of this paper. I have also benefited from discussions with Patrick Forber and Said Saillant Montisano.

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Koon, J. The epistemology of evolutionary debunking. Synthese 199, 12155–12176 (2021).

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  • Evolutionary debunking
  • Moral realism
  • Metaethics
  • Evolution of morality
  • Higher-order evidence
  • Calibrationism