15 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. [Keywords: evolutionary debunking, moral realism, meta-ethics, evolution of morality, higher-order evidence, calibrationism]
…Sharon Street (2006, 2015) and Richard Joyce (2006, 2013, 2016) have both advanced evolutionary debunking arguments which purport to show that, if moral realism is true, our moral beliefs are systematically unjustified. These arguments are motivated by recent empirical work on the evolution of morality, work which suggests that the human moral sense was selected chiefly to promote cooperation among small tribes of hunter-gatherers in our distant evolutionary past. If, however, our moral sense evolved due to the positive contribution that cooperation made to our ancestors’ reproductive fitness, it becomes something of a mystery how it could also succeed in tapping into a well of mind-independent moral truths. It seems like it would be an extraordinary coincidence—in Street’s words, nothing short of a miracle—if evolutionary forces indifferent to the moral truth somehow shaped our faculties to be appropriately sensitive to it.
…This concludes my case for the thesis that evolutionary debunking arguments, properly formulated, present a powerful challenge to moral realism. I have said little, however, about how I think we should conceive of morality, if it is not to be construed realistically. Although I do not have space to discuss my own views at any length here, I suggest we should take seriously the proposal that morality is an adaptive illusion, one built into our minds by natural selection in order to facilitate cooperation among our hunter-gatherer ancestors. Thus, the metaphysics of morality is the metaphysics of illusions, the epistemology of morality is the epistemology of illusions, and the semantics of morality is the semantics of illusions. I do not believe morality is unique in this respect—I follow Daniel Dennett (1991, 2013, 2016, 2017) in thinking that much of our conscious interface with the world, what he calls the manifest image, is an illusion created by selection to aid us in navigating our physical and social environment. It takes only a little reflection on the aim and workings of natural selection to convince yourself that this might be so. Selection’s focus on survival and reproduction is single-minded and absolute; it has no special love for truth, and it will eagerly pack our minds with illusions, other evolutionary constraints permitting, whenever doing so contributes to our reproductive fitness. It should come as no surprise, then, if the moral sense, which presents itself as a window onto a mind-independent domain of morals, instead turns out to be a sham mirror pointed squarely back into our evolutionary past.