Value pluralism is a brute fact that any serious ethical theory has to deal with somehow, and so far as I can tell there are only three ways to do so:1. Subjective values are are all there is, and there is no objective fact of the matter about what’s good or bad.
2. There really is only one true Good, and when people pursue anything else it’s simply due to error.
3. There are lots of things that are good and bad, and these things aren’t reducible to a single underlying variable.
Position (1) is usually taken by libertarians of an economistic bent, but is unsatisfactory when we consider meddlesome preferences because it doesn’t allow us any basis on which to discuss and evaluate states of affairs: I want this and you want that, and where these conflict we have to hash it out either by votes or violence. Position (2) is the one taken by members of various One Big Thing schools of thought, like utilitarianism and Objectivism, but runs into epistemological difficulties.
So far, all I can add is amen and hallelujah (although I'd say there are better arguments against Position 1 and maybe Position 2). But then we get this:
Position (3) appears to be Will [Wilkinson]’s, and strongly informs his contractarian reasoning: if there’s no consensus on value, the best we can do is to build a neutral framework in which people’s pursuit of multifarious values can be accomodated to the maximum extent possible.
If this is a fair statement of what WIlkinson is arguing, the fallacy is obvious. It starts by saying there is no summum bonum, no meta-value, and then it turns around and makes consent the meta-value.
Once you accept value pluralism, then you have to accept that any argument about how we should order our affairs has to be specific to the situation we find ourselves in. You might as well abandon hypothetical consent, and accept that actual consent is usually going to have to give way to something else. In fact, you ought to abandon "political philosophy" in the sense of designing trans-historical principles to evaluate societies by.
(To be fair, McIntosh says he is going to distance himself from this position later.)