This is a belated follow-up to the earlier post addressing an excellent set of questions and challenges raised by Justin Clarke-Doane (NYU) (hereafter JCD) to my claim that Nietzsche argues for moral skepticism by appeal to the phenomenon of moral disagreement. JCD's first set of objections (discussed earlier, with replies by JCD in the comments) raised worries about the extent to which disagreement in ethics was different from disagreement in mathematics--which might warrant anti-realism about the latter or be thought a reductio of the former strategy of argument (assuming that realism about mathematics seems irresistible). In his second set of comments, JCD raises some more general reductio style challenges to the strategy of argument from disagreement. He raises, it seems to me, two very interesting issues:
1. First, JCD points out that philosophers have had significant disagreements about a range of issues, from common-sense claims about the reality of midsize physical objects, to claims about the structure of spacetime, to meta-philosophical claims about philosophy itself. Should we infer skepticism about the subjects in question from these facts about disagreement? Of course, the argument I am concerned with holds that the best explanation of persistent and intractable disagreement is skepticism that there is any fact of the matter about the subject of disagreement. JCD's examples warrant different treatments depending on the facts of each case.
For example, there was not persistent and intractable disagreement about the non-Euclidean character of spacetime: Kant thought it obviously false, and now everyone realizes that Kant was wrong. Disagreement about (as JCD calls them) "first-order intuitively metaphysical claims" (e.g., the existence of properties or possible worlds) probably does warrant the skeptical inference, so there I am happy to "bite the bullett" (and to do so in Nietzschean terms, e.g., I assume philosophers' metaphysical sympathies track underlying moral commitments, which are themselves explicable psychologically). Disagreement about "intuitively common-sense claims" (e.g., about the existence of table and chairs) does not strike me as either persistent or intractable: skepticism about tables and chairs is now a decidely minority viewpoint (I think I can count the philosophical skeptics on one hand!), and the minority's existence seems more easily explicable sociologically (e.g., there are professional rewards for staking out crackpot positions) than by genuine epistemic uncertainties.
Now JCD acknowledges that there are differing degrees of disagreements about his examples (I have not mentioned all of them, just what I hope is a representative sample). But he makes two points that deserve response. First, JCD notes that "the mere possibility that philosophers have held conflicting views with respect to a given claim in the absence of a cognitive shortcoming seems to me to be just as worrisome as the actuality of this." But this can't be right, since it is central to the argument for moral skepticism that disgareements be persistent and intractable, characteristics that are highly probative of as to what explains the disagreement (e.g., a cognitive shortcoming or the absence of any fact of the matter). Second, JCD notes, fairly enough, that "there has been less disagreement among philosophers with respect to some moral claims" than some of the issues noted above (e.g., the metaphysical and common-sense claims); he gives, though, as an example of a moral claim which has generated less disagreement the following: "the claim that one ought not cause needless harm." This, it seems to me, just obscures the fact that the disagreement here concerns the notion of which harms are "needless," a disagreement which is surely a moral one.
JCD raises a second general issue: namely, whether disagreement among philosophers is really relevant to an explanatory argument for skepticism. As he notes, one might think the "virtual unamity among *physicists* with respect to the claim that spacetime is non-Euclidean" is far more important than disagreement among philosophers about the same subject-matter. Of course, it was precisely developments in physics that put an end to the disagreement among philosophers. But putting that to one side, one might worry that philosophical disagreements about subject-matter X are particularly amenable to non-realist explanations, even when X itself is the object of considerable agreement among non-philosophers. (In any case, that is how I understand JCD's interesting challenge.) As JCD notes, even I concede that philosophical disagreements about morality "often fail to translate into disagreements over what is right or wrong in concrete cases" which might suggest that the philosophical disagreement is "at far remove from the day to day moral discussion." If the "folk" (or the scientific folk) can agree about X, why think philosophical disagreement counts against realism about X? That, I take it, is JCD's worry.
So framed, I think JCD's point is correct: it is part of the reason I do not think skepticism about the non-Euclidean structure of spacetime is warranted. Kant's intuitions about spacetime yielded before work in mathematical physics, as it should. (Mathematical physics has more cognitive content than philosophy, one might suppose.) But does the same general point tell against moral skepticism? Here, I think, the matter is more complex. First, it is not like the 'folk' have the kind of convergence in moral opinion that the physicists have in opinion about the non-Euclidean structure of spacetime. Second, the existence of diagreement among the 'folk' about moral matters is precisely what pushes the issues back one level, to the philosophical realm: the philosophical disagreement tracks, at a more abstract level to be sure, the folk disagreement. And yet the philosophers, despite all their 'advantages' (of time, education, insulation from external pressure etc. etc.), still fail to resolve the foundational issues. To be sure, if there were a "moral physics" converging around certain propositions, then the skeptical argument would face a problem: but the only candidate for the "moral physics" is the work of the moral philosophers, and that is precisely the data on which the skeptical argument from disagreement relies!