The second dimension of the four-fold abductive moral argument on offer is moral knowledge. Moral truth is one thing, moral knowledge another. There are numerous ways to approach this matter; we’ll focus on a particular claim that Darwin made. Plenty of folks nowadays think that morality can be fully accounted for by evolution, a claim that can be submitted to critical scrutiny from the direction of moral knowledge.
Angus Menuge explains that a commonality across evolutionary ethics (EE) is the claim that the moral sense of human beings finds its origin in their natural history. In other words, on EE, the shape of our moral sense could have looked quite different. As Darwin puts it,
In such a scenario, (select) acts of fratricide or infanticide might have been thought of by humans as downright obligatory, rather than proscribed.
Menuge has made a useful distinction here, which we noted earlier. He observes that Darwin can be taken in two different ways. “Weak evolutionary ethics,” or “weak EE,” says that, if we had been raised like hive bees, only moral psychology—our moral beliefs—would have changed. In other words, even if we didn’t think so, fratricide and infanticide might still be prohibited. On the other hand, “strong EE” says that natural history dictates moral ontology (what actually is right and wrong). If “strong EE” is the case, our being raised like hive bees would make fratricide and infanticide right.
Strong EE’s main problem is that it makes anything like human rights objectionably contingent. The notion of human rights and dignity disappears under these new hive-bee-like conditions. This presumably stands at radical variance with what’s taken to be unquestionably true about ethics.
The Epistemic Challenge
Whereas strong EE suffers from an ontological challenge, weak EE suffers from an epistemic one. Again, weak EE offers a theory of moral psychology. Although it’s consistent with the existence of objective moral truth and human rights, it faces an impossible difficulty explaining knowledge of such realities. Remember that on weak EE, our belief in the rightness of fratricide and infanticide, not the nature of moral reality itself, is all that changes based on our being raised like hive bees. Even if the beliefs in question turn out to be true, weak EE provides no foundation for trusting our insights about moral reality. In fact, it gives us reason to think we couldn’t. In weak EE biological adaptedness (what is biologically good for the species or individual) and the moral good have no logical connection. If this is the case, Menuge concludes, it seems improbable—given the sweeping number of possible natural histories allowed by an evolutionary model—that the mechanism we have for forming belief would be likely to track moral truth.
Menuge is just one contemporary thinker who has used evolution to call moral knowledge into question. Alvin Plantinga is known for calling all knowledge into question on the joint assumption of naturalism and evolution. For now our focus is just on moral knowledge. The challenge that concerns us here pertains to the dependence of moral beliefs on whatever is relevant in making morality true. Our task is to consider the way in which belief tracks reality. If such a dependence relation fails to obtain, then a tracking relation has not been established to show that our moral judgments depend on actual moral truth. There still may be moral truths, but our justification for our moral beliefs will have been irremediably undermined. And an ethical system that fails to account for our moral beliefs faces serious challenges.
Evolution & Moral Truth
One reason for thinking that such a dependence relation obtains would emerge if the best explanation for a person’s moral belief were to involve the truth of that belief. On evolutionary Darwinism, however, by Menuge’s analysis it would seem that an exhaustive genealogy of our moral beliefs can be provided without addressing whether such beliefs are true. Unless there’s a connection between moral truth and our moral judgments, the dependence thesis is undermined, justification for our moral beliefs is lost, and a “defeater” for moral knowledge has been identified.
Gilbert Harman, Guy Kahane, Sharon Street, Michael Ruse, and Richard Joyce are all examples of recent theorists who have launched a form of the (evolutionary) “debunking objection” against objective moral truth or, more typically, moral knowledge. What all of these variants of the objection have in common is something like this: our moral belief-forming mechanisms are like darts thrown blindly. They are hardly likely to hit the small, distant target of moral truth an ocean away, if there even is such a thing. Evolution is about survival and reproduction, not moral truth.
“Evolution is about survival and reproduction, not moral truth.”
For a very good book-length treatment of an epistemic variant of the moral argument, see Angus Ritchie’s From Morality to Metaphysics. The book’s central contention is that all secular theories that do justice to our most fundamental moral convictions go on to generate an insoluble explanatory gap that consists in their inability to answer the following question: How do human beings, developing in a physical universe which is not itself shaped by any purposive force, come to have the capacity to apprehend objective moral norms?
Ritchie offers a sustained argument worth careful consideration that theism can provide a better explanation of the reliability of our moral cognitive processes. It’s a deeply teleological account of moral knowledge, based on an intentional explanation of our belief-generating and belief-evaluating capacities that track objective moral truth. The power of a personalist account of reality enables the richer teleology that can provide the better account of moral knowledge, without the need to deny that the processes described by evolutionary biology explain the generation of human convictions about ethics and their capacity to reason about and refine them.