(Nod to Daniel for starting me thinking about this topic this morning.)
Suppose that epistemically normative claims are made true by the same facts as certain natural-sounding claims (even though the former do not necessarily 'mean the same' as the latter in any other sense).
And suppose that, on Epistemic Twin Earth, people's use of (what sound like, and are treated like) epistemically normative terms is regulated by natural properties distinct from those which regulate our use of these terms. Perhaps we agree to the sentence: "One epistemically ought not to have beliefs that one knows to be contradictory", and the Twin Earthers dissent from a sentence which sounds exactly like this. Do the people on Epistemic Twin Earth disagree with us about what epistemic norms there are?
If the view described above is right, it might seem that they don't, since (presumably) the Twin Earthlings' normative-sounding claims are made true by different natural facts to ours. Hence the appearance of disagreement is illusory, and (for all that's been said so far, anyway) we might both be right.
1. If this is right, should we be worried (as, according to Horgan and Timmons, we should be worried by an analogous result in the ethical case)?
2. Is it right? Nothing is being claimed, on the view under discussion, about the sense-meaning of our terms of epistemic evaluation or how their reference gets fixed. If we have the intuition that people on Epistemic Twin Earth are disagreeing with us in such a way that we could not both be right, then could we allow that their terms of epistemic evaluation pick out the same properties that ours do, despite the fact that their use of these terms is regulated by some other property? It is plausible that the reference of 'water' is fixed in such a way that Twin Earthlings' term 'water' refers to XYZ, not H20. But is a similar claim plausible for terms of epistemic evaluation?