In the spirit of revisiting some past highlights of my posting here and elsewhere, here's what I wrote about moral scepticism on this blog eighteen months' ago.
Moral scepticism is the philosophical position that will most frequently be defended on this blog.
As a moral sceptic should I believe that there is nothing wrong with murder, rape, dishonesty, cruelty, and mayhem ... and ...?
Well, actually no. I certainly don't believe any of those things, and nor should I. I believe there are very good reasons to prefer kindness to cruelty, loyalty to treachery, non-violent resolutions of conflict to violent ones. In fact, I probably share most (though perhaps not all) of the same core moral attitudes as you.
I can't speak for everyone who has ever claimed to be a moral sceptic, but all I mean by the expression is this. A great deal of ordinary commonsense thinking about morality, as well as a great deal of philosophical thinking about it, asserts, or simply assumes, something that is not true, as far as I can see. It asserts - or assumes - that morality is "objective" in a sense that transcends the desires, interests, values, and fears that human beings actually have.
By contrast, I see the moral norms that prevail in particular societies as arising historically from just those sorts of desires, interests, values and fears. Moral norms ("don't murder or lie"; "be kind") can very often be justified, but the justification will need to appeal to actual human desires, etc. Beyond a certain core, morality may be somewhat underdetermined, its detailed content a product of ongoing bargaining and compromise.
This way of thinking about morality may not make a lot of difference for many important purposes, but it does seem, to me at least, to entail some far-reaching changes to the way we think about morality in the abstract. It also affects how we should consider some of the practical moral decisions that arise socially. It can affect what substantive positions in moral philosophy are intellectually supportable. In particular, I think it implies that many of the more peripheral or unusual examples of whether such and such would be the "right" or "wrong" thing to do may not have clear or determinate answers. Again, some conventional moral wisdom may be without plausible justification.
All that said, most of our core commonsense morality can be justified quite easily. For example, it is not going to be terribly hard to justify having a rule that forbids killing people who fear dying, though there is a great deal more to be said about the detail of this - and I doubtless will say more in future blogs.
This seems fairly much right, and may do for practical purposes, but I'd like to be clearer these days in distinguishing descriptive claims about the phenomenon of morality and its roots from prescriptive claims about how we should act, all things considered.
The plausible meta-ethical positions seem to be a group of sophisticated moral relativist theories - the sort of position I associate with Gilbert Harman, David Wong, Neil Levy, Max Hocutt, and others - and the error theories (moral scepticism) of people like JL Mackie, Richard Garner, Richard Joyce, and Joshua Greene. There are various other positions in the same ballpark, such as the sophisticated non-cognitivism of Simon Blackburn. I am sometimes irritated when other philosophers assume that the only theory in this sort of ballpark is the popular but vulgar kind of moral relativism that we are all taught to avoid in first-year ethics courses.
I think the moral sceptics have the best story to tell, since it is difficult for any of the other non-objectivists to avoid identifying an error somewhere in commonsense meta-ethics. In particular, sophisticated relativists are going to have to say that morality is relative to some society, while admitting that this is not what ordinary people within societies think - therefore, they seem committed to the idea that ordinary people within societies are in error about the nature of morality. While the sophisticated moral relativists can ask us to reinterpret moral claims, translating them into a different framework in which they become relativised claims, that does not avoid the niggling fact that we know erroneous thinking is going on (if we accept a theory such as Harman's).
Vulgar relativist theories, of course, have all sorts of problems. Error theories and sophisticated relativist theories try to get around these by distinguishing questions about whether one has reason to support a moral system, or certain of its norms, from whether certain norms are in fact the norms of a moral system. The answer to the first might be "No" even though the answer to the second is "Yes." Or we might have reason to propose social acceptance of a new norm that is not currently a norm of the system.
Making that distinction is a bitter pill for many people to swallow - it may be counterintuitive. However, that doesn't worry me. This is one of the areas of discourse where I'd expect commonsense intuitions to be unreliable, since we are all socialised to think of certain moral norms as just "correct" (and people from the neighbouring society are socialised to think of their moral norms as "correct"). The psychological force of such intuitions need have nothing to do with evidence and everything to do with our nature as social animals, the need for some order and regularity, and so on. I don't see it as in any way a criticism of sophisticated moral relativism or of error theory.
The question is, what do we do once we realise that the moral norms around us (and often internalised by us) are not "correct" in any unproblematic sense? That's where a sophisticated theory is needed (I currently like to call my own version "naturalistic moral pluralism", but it is technically an error theory). Vulgar moral relativism is, of course, a dismal failure at this point.