When I originally said that I would write something else soon about reasons after the piece on argument, I really did mean it. Really. Equally, I did think I would have something interesting to say about Scanlon's 'What We Owe To Each Other' after Thursday night, but we ended up talking about, insofar as we talked about Scanlon, a perhaps rather arcane distinction between desires and reasons (Scanlon's position seems to be that reasons, which he characterises as 'considerations in favour of x', are primitive, in the sense that they cannot be explained by reference to anything else - a reason just is a reason, and if you don't understand that, there's nothing else I can say to you to explain what they are - and that they provide all the motivational and justificatory force required for actions, just as they are more commonly taken to do for beliefs: the difficulty lies in the position of desires, which Scanlon characterises as non-evaluative urges, which could themselves provide information on which reasons might be based, but are not either motivational or justificatory). So I'm not going to talk about what Scanlon says about reasons, although, partly because he is such an impressive and apparently common-sense philosopher, and partly because I'm already rather sympathetic to the objectivist moral stance he is espousing, I think he's right, but what I have said about reasons.
I gave a presentation on my thesis to a graduate research group my department runs on Thursday before the reading group met. This wasn't the first time I've presented to groups of fellow graduates and academics, but it was the first time anyone other than my supervisor had seen substanial parts of the argument in my thesis - and my supervisor had been, quite rightly, given the stage of writing up I was at, more concerned to sort out stylistic issues than the details of the argument. Understandably, I was quite nervous, but I think it went OK: I could have done with producing a hand-out, because I was trying to compress quite a lot of argument into a relatively small space, and I think it was as a consequence a bit difficult to follow at times, but no-one really laid into me (which may of course be because it was difficult to follow, but...). Anyway, much of my argument turns on what count as reasons (without going too much into the arcane details of contemporary anglo-american political theory, I think that what properly count as reasons when considering the basis on which citizens can consent to the coercive authority of the state is wider than a lot of post-Rawlsian theorists do), so I had a few things to say about reasons.
I suppose there are two key claims, which I think are compatible with, and probably follow from, what I said in the post about the good of argument: that some reasons are reasons for all, even if not everyone does think they are reasons, and that assumption, in any form, is not of itself a reason for anyone else. The thought experiment for showing that some reasons are reasons for all involves slaves. If I want to enslave a group of people, their reasons for not wanting to be enslaved - that they will lose their autonomy, be mistreated and so on - seem to also be reasons for me not to enslave them. I cannot merely brush those considerations in favour of them remaining free aside because they are not directly my considerations, but must take them as over-riding any moral case I might have for enslaving the potential slaves. So some reasons are reasons for all. I think we must think this though, or else we will be unable to respond to those who do not take moral considerations seriously: what are we to say to the potential slave-owner who retorts that they do not care about the wellbeing of the potential slaves, if we cannot say 'it does not matter if you care or not, because the reasons they have for not wanting to be slaves are so weighty that you cannot in all good conscience ignore them'? We would be unable to justify our refusal to let people own slaves, or to allow injustices of any sort, because the scope of morality would only be as wide as those who accepted it.
The problem with assumptions comes up in my thesis because of religious groups, and so my examples are to do with them, but this doesn't mean the problem is restricted to them: individuals of any sort of belief are vulnerable to assuming things, and then asserting that those assumptions are reasons for other people. Any bald preference is in this sense any assumption: what I think of x is irrelevant to your reasons, unless I can show that there is good reason for you to also think that of x. This is why religious groups can be a problem for political theorists who value consent, because they have bald preferences in favour of what they take to be the word of God, which we tend not to think can be the basis of consent for other, non-religious, people, but without which, they might be thought to refuse their consent. The way round this problem is just to point out that religious groups have nothing which can show that non-religious people, or members of other religious groups, ought to agree with their claims. There are a lot of conflicting claims about the word of the Lord, and no way to tell between them, as well as the fact that no-one can show that He even exists in the first place to have words at all. Taking the word of God as claimed by any one religious group as a basis for political arrangements would then be like taking the word of someone chosen at random as such a basis, if not worse, because the person chosen at random could probably point to considerations in favour of their claims, whereas a religious person is operating on a necessarily private faith alone. All this is equally clear of bald preferences though: what matters is that support can be given to the claims in question.
Some one like Posner is here going to say that I'm begging the question, that at root, all that lies at the bottom of my conviction that slavery is wrong is that I believe that slavery is wrong, not any independent fact about the matter. This answer has a lot of rhetorical force, because there will, almost inevitably, come a point at which I am going to have to resort to, if questioning is persistent and anal enough, just stipulating some moral claim: causing physical harm to other people is wrong, or not letting people shape their own lives is wrong. I don't think this shows that there aren't reasons though: it shows that we can't show to someone who does not share our most foundational moral beliefs that those moral beliefs are correct. Given what I've said about being able to justify our beliefs to others, those two things might seem to be the same: after all, if I can't convince someone of something, that's at least a prima facie reason to reconsider my position on it, providing they are being reasonable, taking my arguments seriously and so on.
What Posner misses, though, is the way that outside of a common universe of meaning, there are no independent facts - or if you prefer, merely facts - about anything at all, because we are literally being senseless unless we can ground the meaning of our utterances in some agreed framework. If I refuse to accept that 1+1=2, showing that any of the rest mathematics is true is going to be incredibly difficult, just as, if I am prepared to posit the existence of goblins inside a car engine despite evidence to the contrary, proving that the internal combustion engine functions in the manner we know it does is impossible. The point of the post-Wittgensteinian linguistic turn in philosophy is to force us to realise that we must work within existing frameworks: there is nothing immune to skeptical doubt, and nothing that can be said against or in favour of anything, unless we are prepare to use the concepts we have got in something close to their normal sense. This is not necessarily conservative, because we can, using the connections between concepts, reform and restructure the webs of meaning in which we live, but it does rule out radical skepticism, including radical moral skepticism. Thus, it's just part of the meaning of 'causes harm to other sentient being' that it is pro tanto wrong, and part of the meaning of 'what is all things considered wrong' that I should not do it.