As discussed in chapter 1, the so-called Benacerraf problem goes back at least to Paul Benacerraf’s (1973) “Mathematical Truth”. As its title suggests, Benacerraf was worried about the epistemology of mathematics within a Platonist conception of mathematical objects. The gist of Benacerraf’s argument is straightforward. Benacerraf (at least in 1973) accepts a causal constraint on a theory of knowledge. On a Platonist conception, mathematical objects have no causal power. So if Platonism were true, mathematical knowledge would be impossible. An obvious initial worry here is that causal constraints on knowledge (or justification) have largely fell out of favor.5 But the argument has remained influential, because even if the problem isn’t the causal
inefficacy of Platonic objects per se, there does seem to be a serious mystery about how we could have any epistemic access to abstracta of that sort, causal or not.6
While Benacerraf was concerned with the case of mathematical knowledge, a similar sort of problem arises for non-naturalist moral realists, according to which moral properties are not causally efficacious.7 This parallel was first noticed by Gilbert Harman (1977). And again, as in the mathematical case, even while causal conditions on knowledge have fallen out of favor, there is still a widespread sense that explaining our epistemic access—in terms of responsiveness to the moral facts—is a serious concern for
5 For an overview and references, see Jenkins Ichikawa & Steup (2012).
6 Field (1989), Cheyne (2001), and Liggins (2010) for discussions of this point and developments of Benacerraf’s problem.
7 E.g. Heathwood (2015, p.3), McGrath (2014, p.186), and Scanlon (2014). Oddie (2005) is an exception to this general rule, advocating a version of non-naturalism according to which the non-natural properties are causally efficacious.
the non-naturalist moral realist. Part of the challenge here is just to understand what kind of explanation is being called for. While there is certainly dispute about that, I think it’s overwhelmingly plausible that there is something of real concern in the ballpark of Benacerraf’s original worry. Non-naturalists shouldn’t be satisfied to wait until a clear consensus emerges on the question of what epistemic access comes to before giving a positive epistemological story which assuages these concerns.
On the other hand, a more specific sort of undercutting defeater for moral knowledge comes in the form of evolutionary debunking arguments (EDAs).
Evolutionary debunking arguments are a relative of Benacerraf-style objections. Though they have almost certainly been around much longer, interest in EDAs has skyrocketed largely as a result of the work of Sharon Street (2006) and Richard Joyce (2001, 2006). The details of Street and Joyce’s (as well as other debunkers) EDAs differ in important ways. At the most abstract level, the idea of an EDA is to provide a genealogy of our moral beliefs or belief-forming mechanisms in terms of the fitness-enhancing
evolutionary nature of those beliefs or belief-forming mechanisms. Such an explanation, the debunker argues, will make no appeal to any mind-independent moral facts. This tells us that the moral beliefs or belief-forming mechanisms that we have are, given the wide variety of (conceptually) possible moral systems, extremely unlikely to be tracking the moral facts. This knowledge of almost certain unreliability serves to undercut any justification we initially had about stance-independent moral facts.
In the above, I’ve provided nothing more than the briefest of sketches of Benacerraf arguments and EDAs. But I think it’s clear that these challenges are, if not the same, at least closely related. Both of them are tightly connected to two ideas. First, if the explanation of our moral beliefs or moral belief-forming mechanisms do not invoke some connection to the moral facts, then we should be skeptical about our
prospects for moral knowledge. And second, if moral facts have the metaphysical status that non-naturalists believe that they do, then it is difficult if not impossible to see how an explanation of our moral beliefs or belief-forming mechanisms could invoke the moral facts.
Such is the general outline of the two challenges, but we’ll need to precisify before we can fully assess their chances at success. In the next section, I provide three potential ways of precisifying these sorts of challenges. Each precisification is distinct and compelling enough that it requires a distinct response, which I attempt in sections 4-6. But first, I recap the AEI, which will be doing some of the heavy lifting below. 2. A Posteriori Ethical Intuitionism: An Outline8
AEI consists in two substantive claims. First, AEI is a version of Ethical Intuitionism: EI: “[N]ormal ethical agents have at least some non-inferentially justified first-order ethical beliefs.”
8 This section is largely overlap from my “A Posteriori Ethical Intuitionism and the Problem of Cognitive Penetration” [Ch. 5].
As stated, EI is just the claim that foundationalism—understood in the epistemologist’s sense— is true of the structure of at least some ethical beliefs, and that some ethical beliefs are members of the set of foundational beliefs. However, EI does not entail what we might call Classic
Intuitionism, the claim that the non-inferentially justified ethical beliefs are grounded in intuitions, whatever those turn out to be. EI has its unfortunately misleading name presumably
because most defenders of EI have also been defenders of Classic Intuitionism. I continue to label EI as such in order to accord with what has now become standard usage in the literature. The second claim that constitutes AEI is Ethical Empiricism:
EE: The non-inferential justification of first-order ethical beliefs is grounded in the instantiation of evaluative properties in some kind of perceptual experience.
According to EE, non-inferentially justified ethical beliefs are justified analogously to non-moral perceptual justification, on one sort of traditional foundationalist view. The basic picture is as follows. Under certain circumstances, evaluative properties (or their instantiations) figure in the contents of perceptual experience. Furthermore, at least sometimes, the evaluative properties that figure in the contents of perceptual experience are capable of providing non-inferential
justification for beliefs about the instantiation of evaluative properties. This is compatible with the claim that sometimes evaluative perceptual experiences fail to non-inferentially justify. First, there may be defeaters for the justification that an evaluative perceptual experience would otherwise provide. Second, some evaluative perceptual experiences may be epistemically dependent in the sense that they can’t provide justificatory force independently of some prior evaluative belief. AEI only claims that, in at least some circumstances, neither of these things holds. When they do not, an evaluative perceptual experience can ground a non-inferentially justified moral belief.
AEI is not a single view but a family of views. I briefly note two recently discussed versions of AEI. According to Perceptual Intuitionism, evaluative properties are perceived in the same way that any non-moral but otherwise high-level properties are perceived. For example, the Perceptual Intuitionist may contend that the property goodness is capable of triggering a recognitional disposition within the visual processing system. On the other hand, according to
Affectual Intuitionism, evaluative properties are perceived via affective states, which are
themselves construed as either a form of perception or as a submodule within a broader
perceptual (as opposed to cognitive) system. AEI is compatible with a number of views about the metaphysics of moral properties. However, as the focus in what follows is on epistemological objections to non-naturalist moral realism, I assume that version of AEI throughout.