Any scientific hypothesis that can plausibly be said to bear on the moral realism/anti-realism debate in some sense or another concerns our moral judgements: their evolution, their relation to emotions, the widespreadness of disagreement about them, and so on. The scientific hypotheses underlying science-based arguments for moral realism and anti-realism therefore seem to be contingent on what such judgements are. At first sight this contingency may be deemed unproblematic. If a psychiatrist attempts to investigate the effectiveness of a new drug against depression, or an astronomer attempts to investigate the properties of black holes, they cannot but make assumptions about what it is to suffer from depression or to be a black hole either. So isn’t the apparent contingency of the empirical on the conceptual just a general feature of scientific research?

While this is indeed true, in the context of science-based arguments for moral realism and anti-realism the above-mentioned contingency nevertheless seems to be especially problematic. In particular, it has been claimed to give rise to two related problems: the controversiality and the theoretical neutrality problem.

The controversiality problem

Compared to depression, black holes, and many other subject matters of scientific study the meaning of the term “moral judgement” is much more controversial.Footnote 18 For example, philosophers disagree about whether such judgements must be about harms or benefits (see, e.g., Foot 1978 vs. Haidt and Joseph 2007); whether they entail categorical reasons for action (see, e.g., Kant 1993 vs. Foot 1972); whether and in which sense they entail motives to act according to them (see, e.g., Smith 1994 vs. Svavarsdóttir 1999); and so on. By presupposing a theory of the nature of moral judgements scientific studies hence threaten to become conceptually controversial themselves. Any critic of these studies (and of empirical and metaethical positions which they are supposed to support) may question their results on grounds of their failing to address moral judgements.

Richard Joyce has recently noted this “controversiality problem” with regard to the hypothesis that moral judgements are adaptations:

[...] the notion of moral judgment is sufficiently pliable as to allow of different legitimate precisifications. [...] It is possible (and not unlikely) that on any precisification of “moral judgment” [...] moral nativism is false. But it is also possible that moral nativism is true for certain precifisications and false for others. Certainly the plausibility of various pro-nativist and anti-nativist arguments varies according to different conceptions of the target trait [...].Footnote 19 (Joyce 2013: p. 566)

The theoretical neutrality problem

The meaning of the term “moral judgement” does not only depend on these judgements’ relation to reasons, motivation, etc., but also on whether such judgements purport to represent (objective) moral facts. In testing empirical hypotheses about these judgements scientists may therefore have to (implicitly) accept the semantic presupposition/s of one or several variant/s of moral realism or anti-realism. This implies that the results of their studies fail to be theoretically neutral with regard to the existence of objective moral truths. These results may hence be unable to ground (strong) arguments in favor of (certain) variants of moral realism and anti-realism.

In addition to several other scholars (see Bruni 2011; Joyce 2008: p. 387; and Bennett and Hacker 2003: p. 2 in a non-moral context), this “theoretical neutrality” problem has recently again been pointed out by Antti Kauppinen:Footnote 20

[...] conceptual questions are inescapable and precede the empirical ones: to find out what leads to moral judgment or what brain states are correlated with it, we must first know what counts as a moral judgment. [...] this is [...] to say that [...] this work [scientific work] does not advance our understanding of the nature of moral thinking. [...] when we are trying to understand what it is to think that something is morally wrong, there are no harder data than convincing stories and plausible descriptions [...]. (Kauppinen 2008b: pp. 23–24)

The worry at issue, then, is that scientific investigations of moral judgements require an ex ante theory of the nature of these judgements, and that such investigations are accordingly conceptually controversial (Joyce) and/or biased against (particular variants of) moral realism or anti-realism (Kauppinen).

The Logical Priority Objection

(P1) : In testing empirical hypotheses about moral judgements scientists must make assumptions about what it is to make a moral judgement. (P2) : Theories about what it is to make a moral judgement are highly controversial and/or entail or suggest (variants of) moral realism or anti-realism. Ergo:: Scientific evidence about moral judgements is highly controversial and/or fails to be theoretically neutral with regard to moral realism and anti-realism. It thus cannot ground (strong) arguments about these views.

The controversiality and theoretical neutrality problems have important implications for the scientific approach to the existence of objective moral truths. However, like the other meta-theoretical objections considered in this paper, they fail to ground this approach’s rejection as a whole.

To begin with, there is one kind of scientific evidence which neither needs to be conceptually controversial nor theoretically biased in the way explained above at all, namely evidence about ordinary people’s intuitions about moral concepts, and about the truth of moral realism or anti-realism.Footnote 21 As an example, consider two recent studies by Jennifer Wright et al. (2013, 2014). In these studies Wright et al. attempted to measure intuitions about moral realism and anti-realism by asking subjects for each of a number of sentences whether they regarded it as a moral sentence, and whether they believed the sentence to be “true”, “false” or “just an opinion or attitude”. This measure of folk moral realism lacks in construct validity (see Pölzler forthcoming b). However, and more importantly in our present context, Wright et al.’s studies do not suffer from any of the problems pointed out above (nor would they suffer from them if their measures were to be improved). As to the theoretical neutrality problem, the studies did not involve any ex ante commitment to semantic presuppositions of moral realism or anti-realism. In fact, intuitions about these presuppositions (Are moral sentences truth-apt?) are part of what Wright et al. attempted to measure in the first place. And regarding the controversiality problem, the item sentences that subjects were presented were not classified as moral/non-moral by the researchers, but rather by the subjects themselves. The study therefore did not involve ex ante commitments to any other claims in moral semantics (such as about whether moral judgements are necessarily about harms or benefits) either.

Most science-based arguments for moral realism and anti-realism are based on hypotheses that do not address folk moral semantics or folk moral realism. With regard to these arguments (such as evolutionary debunking arguments, Prinz’s sentimentalist argument, and arguments from moral disagreement) the logical priority objection can have some force. However, it would be exaggerated to conclude that scientific evidence about moral judgements therefore cannot bear on the moral realism/anti-realism debate at all.

First, some scientific findings about moral judgements may hold up on (almost) any plausible account of what such judgements are—whether one takes them to entail categorical reasons or not, whether one takes them to purport to represent (objective) moral facts or not, and so on. Second, in cases in which findings are sensitive to such accounts scientific research on moral judgements may again be understood in a conditional sense. It is still possible to show that if one defines moral judgements in a certain way then a particular hypothesis is scientifically well-supported, and may provide evidence in favor of moral realism or anti-realism (see Nadelhoffer and Nahmias 2007: p. 134). And third, and most importantly, given that both questions about what it means to make a moral judgement and about the truth of moral realism in general are so contested, it seems reasonable to give up on the idea of a strict logical priority of the conceptual over the empirical in the first place.

It is true that one’s theory of the nature of moral judgements may sometimes reasonably lead one to reject the results of certain scientific studies (see Pölzler forthcoming c). Conversely, however, one should allow scientific evidence to bear on the nature of these judgements too. Contrary to one of Prinz’s above-mentioned hypotheses, for example, a significant proportion of judgements that would pre-theoretically widely be considered moral have been found not to correlate with strong emotions (e.g., Greene et al. 2001, 2008; Pölzler 2015). In the face of the controversiality of the nature of moral judgements this finding provides at least some (defeasible) grounds for doubting that such judgements are constituted by occurrent emotions (as, e.g., claimed by Ayer [1936] 1952: p. 107). Moreover, given the plausible assumption that some subjects’ judgements were made under what Prinz considers to be the manifestation conditions of emotional dispositions, the finding even casts doubt on his claim that moral judgements are constituted by dispositions to have emotions (see Pölzler forthcoming c).Footnote 22

Given this more complex relationship between the conceptual and the empirical, I suggest substituting the logical priority assumption with a reflective equilibrium model. Claims about the nature of moral judgements and scientific hypotheses about these judgements must be reflected on as a whole. In particular, they must be continuously mutually adjusted, so as to finally reach a state where they are consistent and support or best explain each other (see Brax 2009: p. 4, 11; Levy 2011: p. W1; Toulmin 1971: 33–37). But even if this goal is reached one must not yet come to an end with one’s investigations. This is because to the extent that the nature of moral judgements or the truth of relevant scientific hypotheses depend on claims about non-moral matters, these claims must be considered as well.

Consider, for example, the question of whether emotions have cognitive content, and hence function to represent facts (see, e.g., Nussbaum 2004 vs. James 1884). If this question is answered affirmatively the claim that moral judgements are constituted by (dispositions to have) emotions turns out much more plausible than if it is answered in the negative. For only if emotions do have cognitive content moral judgements can uncontroversially be said to be robustly truth-apt; embeddable in conditionals, propositional attitude statements, questions, etc.; and able to function as premises and conclusions in arguments (see Geach 1965). Moreover, as proponents of cognitivist and non-cognitivist theories of emotions regard different brain areas as indicative of emotional activity, they may even differ in their interpretation of scientific findings about moral judgements’ mental correlates.

Ultimately, then, advancing our understanding of the existence of objective moral truths requires what has been called a “wide” reflective equilibrium (see Daniels 1979), i.e., we must consider a much more extensive array of evidence than has commonly been assumed.