Ethics 120 (April 2010): 441–464  2010 by The University of Chicago. All rights reserved. 0014-1704/2010/12003- 0003$10.00 441 ARTICLES On the Evolutionary Debunking of Morality* Erik J. Wielenberg I. INTRODUCTION Many claim that the availability of evolutionary explanations for human moral beliefs threatens the view that humans have moral knowledge. Peter Singer suggests that evolutionary explanations can debunk moral claims. 1 Michael Ruse declares: “Morality is a collective illusion foisted upon us by our genes.” 2 Sharon Street and Richard Joyce have recently offered sustained evolutionary debunkings of morality. 3 Proponents of such debunkings endorse the following thesis: The Evolutionary Debunking Thesis (EDT): If S’s moral belief that P can be given an evolutionary explanation, then S’s moral belief that P is not knowledge. 4 * A shorter version of this article was presented at the second annual Rocky Mountain Ethics Congress at the University of Colorado in August 2009. I thank the audience and my commentator Brad Monton for helpful feedback on that occasion. Earlier versions of the manuscript were read and commented on by Matthew Braddock, Ben Bradley, David Enoch, Chris Heathwood, and assorted referees and editors for Ethics. I thank all of these people for their assistance. This article was written with the support of a DePauw University Faculty Fellowship. 1. Peter Singer, “Ethics and Sociobiology,” Philosophy and Public Affairs 11 (1982): 40–64. 2. Michael Ruse, Taking Darwin Seriously (New York: Blackwell, 1986), 253. 3. Sharon Street, “A Darwinian Dilemma for Realist Theories of Value,” Philosophical Studies 127 (2006): 109–66; Richard Joyce, The Evolution of Morality (Cambridge, MA: MIT Press, 2006). 4. A natural question to ask here is, why is the debunking limited to moral beliefs? The answer is that moral beliefs are seen as particularly susceptible to such debunkings because the evolutionary explanations proposed for them typically do not require that they be true. This aspect of evolutionary debunking arguments is examined in Sec. V.