Metaphysics

Putting aside the arguments that appeal to moral disagreement, a significant motivation for anti-realism about morality is found in worries about the metaphysics of moral realism and especially worries about whether moral realism might be reconciled with (what has come to be called) naturalism. It is hard, to say the least, to define naturalism in a clear way. Yet the underlying idea is fairly easy to convey. According to naturalism, the only facts we should believe in are those countenanced by, or at least compatible with, the results of science.

To find, of some putative (предполагаемый) fact, that its existence is neither established by, nor even compatible with science, is to discover, as naturalism would have it, that there is no such fact. If moral realism requires facts that are incompatible with science (as many think it does) that alone would constitute a formidable argument against it.

Noncognitivists and error theorists alike have no trouble respecting naturalism while offering their respective accounts of moral claims. In both cases, their accounts appeal to nothing not already embraced by naturalism. Of course noncognitivists and error theories disagree in crucial ways about the nature of moral thought, and noncognitivists and error theorists disagree among themselves too about which versions of their preferred accounts are better. But they all are, from the point of view of naturalism, on safe ground.

Moral realists, in contrast, are standardly seen as unable to sustain their accounts without appealing, in the end, to putative facts that fly in the face of naturalism. This standard view can be traced to a powerful and influential argument offered by G.E. Moore (1903). As Moore saw things, being a naturalist about morality required thinking that moral terms could be defined correctly using terms that refer to natural properties. Thus one might define ‘good’ as ‘pleasant’, thus securing naturalistic credentials for value (so long as pleasure was a natural property) or one might define ‘good’ as ‘satisfies a desire we desire to have’ or as ‘conforms to the rules in force in our society’ or ‘promotes the species.’ Any one of these proposed definitions, if true, would establish that the facts required to make claims about what is good true or false were compatible with naturalism. Yet, Moore argued, no such definition is true. Against every one, he maintain, a single line of argument was decisive. For in each case, whatever naturalistic definition of moral terms was on offer, it always made sense to ask, of things that had the naturalistic property in question, whether those things were (really) good.

Consider someone who held not merely that pleasure was something good but (as a definition would have it) that pleasure was goodness—that they were one and the same property. According to that person, in claiming that something is pleasant one is claiming that it is good, and vice versa. In that case, though, it would not make sense for people to acknowledge that something is pleasant and then wonder, nonetheless, whether it was good. That would be like acknowledging that something is a triangle and then wondering, nonetheless, whether it has three sides. Yet, Moore maintained, the two cases are not alike. A person who wonders whether a triangle has three sides shows he does not understand what it is to be a triangle. His competence with the terms in question is revealed to be inadequate. In contrast, Moore observed, for any natural property whatsoever it was always an open question whether things that had that natural property were good. A person who raised that question did not thereby reveal himself not to be competent with the terms in question. What this shows, Moore argued, was that moral terms did not refer to natural properties and so a proper account of moral claims would have to recognize that they purport to report non-natural facts.

Now of course moral realists can consistently acknowledge this and then argue against naturalism—perhaps, at least in part, on the grounds that naturalism is incompatible with acknowledging moral facts. This was, in fact, Moore’s position. Yet one then has the burden of explaining how moral facts are related to natural facts and the burden of explaining how we might manage to learn of these non-natural facts. A good deal of the work that has been done defending moral realism is devoted either to meeting these burdens or to showing that they do not pose a special problem just for morality. Moral realists of this sort allow that moral facts are not natural facts, and moral knowledge is not simply of a piece with scientific knowledge, even as they defend the idea that there are moral facts and (at least in principle) moral knowledge. They thus reject the idea that science is the measure and test of all things (Shafer-Landau 2003, Parfit 2011, Scanlon 2014).