by Michael Lopresto
Moral realism is sometimes challenged on scientific grounds, namely that we can't fit value into a scientific world view. I've addressed this concern before, as part of a distinctively philosophical project often described as reconciling the manifest image with the scientific image. However, moral realism has recently come under a new sort of attack on scientific grounds, put most forcefully and ingeniously by Sharon Street. The argument begins from the empirical premise that evolutionary forces have influenced our moral beliefs, something that is plainly true, to a sceptical conclusion that our moral beliefs are unjustified. So the argument is essentially that since moral beliefs were not caused by moral facts, we have no reason to think that our moral beliefs could be true.
Firstly, some clarifications are in order. What distinguishes the evolutionary debunker from other anti-realists is that she is not trying to show that there are no moral facts, but rather that there is no moral knowledge. Furthermore, what distinguishes the evolutionary debunker is that her premises are empirical, and that such empirical premises entail that our moral beliefs have a highly suspect origin. So this is an epistemological argument for moral scepticism. However, this may also be taken as a reductio of moral realism, since moral realism would be rather useless indeed if no moral facts could ever be known.
So let's examine the premise that the origins of a belief could undermine its justification. In good cases of belief formation, our beliefs are often caused by the things that they are about. For example, I currently believe that there are about three dozen books in front of me. This belief is caused by my perception of the books themselves, and as far as I know, my perceptual faculties are working pretty well. But consider a case where I take a hallucinogenic drug and start hallucinating books in front of me without even knowing it. I would have the exact same belief, that there about three dozen books in front of me, but rather than being caused by the books themselves, the belief is caused by the drug. Therefore, the belief is not justified because it's not caused in the right way, even if the belief is true just by chance.
Take another example. I know that Napoleon lost the Battle of Waterloo because there has been a causal chain beginning in the observation of those present at the event, to testimony that has been passed on from one person to another, causing me to know it. There has been a causal chain mediated by testimony from 1815 to the present, if you will. Now imagine the hypothetical case where I've grown up in a society that's never mentioned Napoleon or the Battle of Waterloo. However, one day I happen to take a drug that caused me to believe that Napoleon lost the Battle of Waterloo. I don't know that Napoleon lost the Battle of Waterloo, since the belief is just lucky—it's not caused in the right way. These examples show that the origins of belief matter, especially for ruling out lucky true belief as cases of knowledge.
To illustrate the epistemology within the argument, I'll use an example from Katia Vavova's (2015, p. 105) insightful paper, whereby you might come to doubt your belief that the wall in front of you is green:
Optometrist: Your optometrist says that your colour vision might be deceiving you: the tests suggest you are blue-green colourblind.
Sceptic: The sceptic says that all your senses might be deceiving you. She has done no tests.
What's the fitting response to the optometrist and the sceptic? Naturally enough, it is to take the optometrist seriously, and not the sceptic (although our epistemology needs to explain why the sceptic is wrong, of course). After all, the optometrist has provided empirical evidence for her claim, and the sceptic has provided no evidence whatsoever. Thus we can understand the evolutionary debunker's challenge as being much more like the optometrist's than the sceptic's. The optometrist's challenge is empirical and specific, rather than being a priori and general, like the sceptic's. Thus the debunker must provide evidence of error.
The debunker can put her evidence in a number of steps, perhaps beginning with the premise that the human mind is the product of natural selection. Natural selection is the only remotely plausible explanation of biological complexity, and the human mind is the most complex biological mechanism on the planet. However, the mechanisms of natural selection are driven by fitness and survival, and truth doesn't enter the picture. Furthermore, it is plausible to explain many of our evaluative attitudes as being shaped by natural selection. All humans feel disgust at the thought of incest, feel special obligations to loved ones, judge that freeriders ought to be punished, and so forth. Offspring produced from incest have less fitness than those who are not, favouring loved ones promotes one's own genes through kin selection, and punishing freeriders increases the fitness of the group. So it's at least prima facie plausible that many of our evaluative attitudes originate from evolutionary forces.
There are other explanations for our moral beliefs and evaluative attitudes, as Sharon Street (2006, p. 122) points out:
[I]t's possible that as a matter of sheer chance, some large portion of our evaluative judgments ended up true, due to a happy coincidence…, but this would require a fluke of luck that's not only extremely unlikely, in view of the huge universe of logically possible evaluative judgments and truths, but also astoundingly convenient to the realist.
So the burden of proof is now on the realist to show why her beliefs are not just a complete fluke. But as Vavova perspicaciously notes, this particular argument is no longer evolutionary. Indeed, it is no longer even empirical. The argument here is based on two main points: we have one set of moral beliefs, and yet the space of possible moral beliefs is absolutely huge. Against the moral sceptic, there is no non-question-begging evidence that rules out the moral beliefs we don't hold as being false. So the problem for the debunker's argument at this stage is that if her argument applies to our moral beliefs, a fortiori, it applies to all our beliefs. For example, we hold the belief that 2 plus 2 equals 4. And yet there are indefinitely many other mathematical beliefs we could hold instead of this one. And yet it would be absurd to apply this argument to our mathematical beliefs in addition to our moral beliefs.
Hence, Street goes on to say:
…our system of evaluative judgments is revealed to be utterly saturated and contaminated with illegitimate influence. We should have been evolving towards affirming the independent evaluative truths posited by the realist, but instead it turns out that we have been evolving towards affirming whatever evaluative content tends to promote reproductive success. We have thus been guided by the wrong sort of influence from the very outset of our evaluative history, and so, more likely than not, most of our evaluative judgments have nothing to do with the truth.
So here we have a powerful empirical, evolutionary challenge to the realist. I don't intend to settle the issue here—that would take a whole book, after all—but I think there is some truth and some falsity contained within the argument. The truth regards many of our evaluative attitudes, which are profoundly off the mark. Consider Jonathan Haidt's research concerning judgments about incest. An example of a situation is presented to subjects which involves incest, where there is no possibility of children being produced, or bad consequences. The majority of subjects judge the action to be morally wrong, and when pressed for reasons, they confabulate until they're dumbfounded. On the other hand, consider the research presented in Steven Pinker's towering work The Better Angels of our Nature, in which he documents the dramatic decline of violence over human history. One way of reading this remarkable finding is that as natural selection has played less of a role in human life, and cultural evolution, culture and experience have taken over, our moral beliefs get closer and closer to the truth. Of course, this on its own won't be enough to convince the moral sceptic, but it's a start.