Andreas Mogensen All Souls College, Oxford Faculty of Philosophy Evolutionary debunking arguments in ethics A thesis submitted for the degree of D.Phil in Philosophy Hilary Term 2014 University of Oxford 1 Andreas Mogensen, All Souls College, Oxford; Faculty of Philosophy Evolutionary debunking arguments in ethics D.Phil Submission, Hilary 2014 Abstract: I consider whether evolutionary explanations can debunk our moral beliefs. Most contemporary discussion in this area is centred on the question of whether debunking implications follow from our ability to explain elements of human morality in terms of natural selection, given that there has been no selection for true moral beliefs. By considering the most prominent arguments in the literature today, I offer reasons to think that debunking arguments of this kind fail. However, I argue that a successful evolutionary debunking argument can be constructed by appeal to the suggestion that our moral outlook reflects arbitrary contingencies of our phylogeny, much as the horizontal orientation of the whale’s tail reflects its descent from terrestrial quadrupeds. An introductory chapter unpacks the question of whether evolutionary explanations can debunk our moral beliefs, offers a brief historical guide to the philosophical discussion surrounding it, and explains what I mean to contribute to this discussion. Thereafter follow six chapters and a conclusion. The six chapters are divided into three pairs. The first two chapters consider what contemporary scientific evidence can tell us about the evolutionary origins of morality and, in particular, to what extent the evidence speaks in favour of the claims on which debunking arguments rely. The next two chapters offer a critique of popular debunking arguments that are centred on the irrelevance of moral facts in natural selection explanations. The final chapters develop a novel argument for the claim that evolutionary explanations can undermine our moral beliefs insofar as they show that our moral outlook reflects arbitrary contingencies of our phylogeny. A conclusion summarizes my argument and sets out the key questions that arise in its wake. Word count: 74,900 2 Acknowledgments: For helpful comments and discussion of my work in this essay, I am grateful first and foremost to my supervisors, Krister Bykvist and John Hawthorne, and to Matthew Braddock, Daniel Deasy, Hilary Greaves, Cecilia Heyes, William MacAskill, Walter Sinnott-Armstrong, Amia Srinivasan, and Ralph Wedgwood. I thank All Souls College for supporting my research. Last but not least, I am indebted to Nicola Mastroddi for her love and support. 3 Evolutionary debunking arguments in ethics Table of contents 0. Introduction 5 1. The evolutionary origins of morality: considering the evidence 24 2. Interpreting the evidence: Functional Truth-Irrelevance and Phyletic 71 Contingency 3. Ockham’s Razor, Sensitivity, and the Total/Functional Fallacy 98 4. The Coincidence Problem: a skeptical appraisal 129 5. “The dissentient worlds of other people”: phylogeny, contingency 179 anxiety, and the epistemology of disagreement 6. Epistemic reasons and persons: disagreements in moral intuition as 209 defeaters 7. Conclusion and directions for future research 238 Bibliography 249 4 0. Introduction 1. Introduction Can evolutionary explanations debunk our moral beliefs? In this essay, I offer new reasons to think that this question should be answered in the affirmative and that previous arguments to that effect have been flawed. In this introduction, I’m going to unpack the question, offer a brief historical guide to the philosophical discussion surrounding it, and explain what I mean to contribute to this discussion. The unpacking will be done in section 2, beginning with an outline of some relevant epistemological presuppositions, moving on to consider what qualifies as an evolutionary explanation, and finally addressing whether we should understand our question as encompassing all moral beliefs or just a particular subset. In section 3, I then discuss the history of evolutionary debunking arguments from Darwin to today, noting an important shift in focus with respect to the question of why evolutionary explanations are considered debunking. Finally, in section 4, I outline the aims and structure of this essay. 2. Unpacking the question 2.1 Epistemological presuppositions We are to consider whether our moral beliefs can be debunked by evolutionary explanations. What is it for a belief to be debunked in this sense? My emphasis throughout this essay will be on how evolutionary explanations reflect on the justification (or lack thereof) of our moral beliefs. I assume that the question of 5 justification is intimately connected to normative and deontic questions about what we ought to believe and what we are permitted to believe. In particular, I assume that being justified in believing p is a necessary condition for being permitted to believe p and for it to be the case that you ought to believe p. In choosing to focus on justification, I am to some extent attempting to impose order. Epistemic evaluation is not confined to questions of justification: we can ask whether we know the things we believe, whether our beliefs reflect various epistemic virtues and vices, and so on. Whereas some philosophers who believe that evolutionary explanations impact the epistemic status of our moral beliefs are clear that they’re concerned with justification, others are not so easy to pin down;1 some of their critics have chosen to frame the issue in terms of knowledge, rather than justification.2 I believe that where there is uncertainty, a reasonable interpretation of pro-debunking arguments nonetheless finds the issue of justification in play. I can only really substantiate this exegesis in the ensuing chapters, through my discussion of the various extant debunking arguments. However, I can note the following already here. The debunking power of evolutionary explanations attracts philosophical attention because of the felt possibility that we may be forced to make substantial revisions in our moral outlook in light of new discoveries about the evolutionary origins of morality. For that to be so, it must be the case that evolutionary explanations can speak to what we ought and ought not to believe. As I understand the notion of epistemic justification, they can do so only by addressing the justificatory status of our moral beliefs. I’m going to further interpret the notion of debunking via the well-known idiom of epistemic defeat, introduced by John Pollock (1970, 1986). Thus, evolutionary explanations are debunking iff they supply defeaters. A defeater, roughly speaking, is a 1 Joyce (2001, 2006) is admirably clear; Ruse (1986) is not. 2 See, e.g., Brosnan (2011), Wielenberg (2010). 6 condition that provides a prima facie reason to withhold belief from some proposition that we would otherwise have been justified in believing.3 Defeaters are prima facie reasons to withhold belief: they can themselves be defeated by way of conditions known as defeater-defeaters. (There are also defeater-defeater-defeaters, and so on.) Two classes of defeaters are widely recognized: rebutting and undercutting. A rebutting defeater is a reason to believe the contrary of what you believe (or have justification for believing); an undercutting defeater works instead by casting doubt on the trustworthiness of the grounds for your belief (or the method by which it was formed). Thus, the discovery that evidence which we took to support some hypothesis has been doctored will undermine belief in the hypothesis without necessarily providing any positive reason to think the hypothesis is false: this constitutes a merely undercutting defeater. Some defeaters are hybrid: they both rebut and undercut. It’s plausible that many rebutting defeaters are in fact undercutting as well: if I receive evidence that some method of belief-formation I’ve used gives the wrong result (a rebutting defeater) and I have no reason to expect that the method delivers the wrong result due to random error or noise, I receive evidence that the method is systematically biased toward error (an undercutting defeater). Interpreted in the idiom of defeat, the question we are considering asks, in effect, whether evidence we receive about the evolutionary origins of our moral beliefs could affect their justificatory status so as to cancel any pre-existing entitlement that we might have for holding those beliefs. Thus, I’ll assume that we are prima facie entitled to rely on the relevant beliefs, as well as the methods by which they are formed, including basing our beliefs on our moral intuitions.4 Obviously, if the beliefs that admit of evolutionary explanations are unjustified on independent grounds, there 3 A more exact definition of epistemic defeat requires resolving various complications that needn’t concern us here. See the excellent discussion in Kotzen (ms.). 4 For a defence of intuitions as conferring justification on corresponding beliefs see Huemer (2005). Unlike Huemer, I do not presuppose that intuitions are intellectual seemings, as opposed to, say, inclinations to believe. For further discussion of the role of intuitions in moral psychology see ch. 2. 7 is little point in worrying about the debunking power of evolutionary considerations. We should get rid of them in any case. Another question that we might have considered, but which I set aside, is that of whether evolutionary explanations could simply show our beliefs to be and have been unjustified: whether certain facts about the evolution of human moral psychology might make it the case that our moral beliefs are unjustified, quite apart from the capacity of our awareness of these facts to defeat any prior prima facie entitlement. Philosophers who accept some form of Epistemic Internalism would naturally reject this possibility: they take it that the justificatory status of our beliefs supervenes on factors ‘internal’ to the epistemic agent, which rules out any relevance for facts about the distal causes of our beliefs (apart from our awareness of them). Philosophers who accept Epistemic Externalism, however, would not reject this possibility out of hand.