@Oh phil,
Oh! wrote:Those are ways in which I have seen "counterfactual" used, but I am still struggling to fit those concepts into the original sentence I quoted. Can anyone rephrase it in a way that makes it clear what Metzinger was on about?
No idea. It does not seem to be English, at least prima facie.
I imagine that by "counter-factual" he means, "contrary to the facts" or, in plain English, "false". But I really don't know.