Although it really has nothing much to do with NKS, whenever discussing skepticism the moral argument for it comes up. I don’t find those convincing, and I think I should explain why.
Part of the attraction of arguments from epistemic weakness comes from a set of moral claims commonly advanced for them, or against the imagined contrary position of epistemic dogmatism. I don’t consider those common moral claims remotely sound, and their association with epistemic weakness is too loose to bind the two together. Roughly, people think it is intolerant to claim to know, sometimes about specific issues and sometimes anything at all, and more tolerant or nicer somehow to refrain from such claims. As though knowledge were inherently oppressive and ignorance, freedom.
At bottom I think this is a post hoc fallacy, a loose association arising from flip diagnoses of what was wrong with chosen bete noirs. So and so believed he knew something and look how awful he was, ergo… Ergo not very much. Your favorite bete noir probably also thought that 2 and 2 are 4, and never 5 nor 3. This won’t suffice to dispense with the addition table and make arithematic voluntary. Evil men had noses. This doesn’t make noses the root of all evil. Believing you know things is as normal as having a nose.
For that matter, I can comb history and find any number of convinced skeptics who were personally as nasty as you please, or even as intellectually intolerant on principle. Al Ghazali will argue from the impotence of human knowledge that philosophy should be illegal and the books of the philosophers burned. You won’t find any skeptical argument in Hume that he didn’t anticipate by centuries. But in his cultural context, it was the theologians that were the skeptics and philosophers who believed in the possibility of (human) knowledge. As this context makes clear, you need a reason to challenge entrenched convention, and if human thought cannot supply one you are left to the mercies of convention. Convention can reign without making any epistemic claims; it suffices to destroy all possible opposition.
There is a more basic problem with the idea that tolerance requires epistemic weakness. It misunderstands the reason for tolerance, and because of it will narrow its proper domain of application. The real reason for tolerance is that error is not a crime, but instead the natural state of mankind. Tolerance is tolerance for known error, or it doesn’t deserve the name. Imagine some Amish-like sect that wants to opt out of half of the modern world, and believes demonstrable falsehoods, but keeps to itself and bothers no one. What is the tolerant attitude toward such a group?
People can think what they like. You can’t require truth of them as a moral matter, because it is rarely available at all, for one, but also because truth can only be grasped internally, as a freely offered gift. You can’t make someone else think something, and it is a category error to try. Minds are free, and individual. All you can do it offer a truth (or a notion or thought), for someone else to take or leave. In the classic formulation of the age of religious wars in Europe, a conversion obtained by duress simply isn’t a conversion. Yes men err, and sometimes their errors issue in actions that are crimes. But no, you cannot eliminate the possibility of crime by first eliminating error. You couldn’t eliminate error even if you had full possession of the truth (which you don’t, to be sure). Persecution isn’t made any better if the doctrine for which you persecute is rational – it remains persecution. (The historian Ignaz Goldhizer made this point in a convincing Islamic context, incidentally).
Human beings are falliable and they are mortal. They have short lives full of personal cares, trials, and difficulties, whose incidence and urgency are peculiar to each individual. They are born in utter ignorance and dependent on their immediate fellows for most of their categories and systems of thought. They grope for knowledge because they need it in practical ways, they attain bits and pieces of it in scattershot fashion, with more found by all combined than possessed by any specific subset among them. Most knowledge stays distributed, particular, and operational – not centrally organized, general, or theoretical.
You can’t require conformity to some grand theoretical system of men in general without violence to half of them. Equally you can’t deny them the possibility of knowledge without maiming them all; humility for export isn’t a virtue. Real tolerance is a patient acceptance of these facts, a charitable and kindly view of our mutual difficulties. We offer one another such knowledge as we have found, and recipients freely take it or leave it, after judging for themselves what use it may have in their own lives. If instead you try to force everyone to acknowledge that they don’t know anything, one you are wrong because they do know all sorts of things, and two you are exactly requiring the sort of grand theoretical conformity you are pretending to be against. You end up making disagreement with your epistemological claims some sort of crime. In this case, that disagreement isn’t even an error, let alone any crime.
So at bottom, my objection to arguments in favor of epistemic weakness on the basis of its supposed tendency to further moral tolerance is that it has no such tendency, and that it misses the point of true tolerance. Which isn’t restricted to a response to ignorance. It isn’t (just) the ignorant who require tolerance, it extends to people who are flat wrong, but innocently so. The moral requirement to practice tolerance is not limited to people unsure of themselves, but extends to people who are correct and know it. The real principle of tolerance is simply that error is not a crime.