Fontwell, the question here is what you mean by the “wrongness” of a statement. If you mean that the statement is ill-formed or meaningless, many if not most philosophers in the 20th and 21st centuries would agree with you. (In fact, I would too.) But the question is what sort of principled and motivated account we can give to explain why it is ill-formed or meaningless. Just pointing out a problem doesn’t solve it; the question is how you can have a language that allows you to make assertions of the form “A is true,” where A is a name or description that designates a particular sentence, while avoiding the awkward consequence that one of the sentences you might deny is the very sentence by which you deny it. Just banning sentences that lead to contradictions, solely on the basis of their leading to contradictions, has a couple of awkward effects: (1) it seems to be nothing more than linguistic gerrymandering; if I write “Johnson’s thesis is false,” then why should I be able to name it “Jackson’s thesis” but not “Johnson’s thesis”? What’s to stop me? (2) There are in fact self-referential sentences that don’t result in logical contradictions, but do cause philosophical headaches in other ways. Sentences of the form “If this sentence is true, then P” don’t directly result in any contradiction, but do allow you to prove absolutly any proposition whatsoever that you care to substitute for P. M, as discussed above, seems to be a part of our ordinary language, but it also seems to allow for the possibility of the bizarre disagreement between the normal believer and the perverse skeptic. And T, as discussed by Blar, is logically completely compliant — if it’s true, it’s true, and if it’s false, it’s false. But its semantics seem to shrink to a vanishing point; there seems to be nothing even in principle that could make it true, or make it false.
Blar, I think you’re right to show interest in T (in my essay I talk about it as an essential part of understanding what’s wrong with L) but I don’t think that M can be reduced to it. The simple reason being that T can’t meaningfully be asserted but M can (and was, by Marco Polo). I think that part of what a theory has to do in accounting for the “data,” as it were, is to account for the fact that Polo wrote M (or rather, wrote its equivalent in Italian) and we understood what he wrote.
One way to think about this is that when we evaluate M (and so, if we try to evaluate your looped case of M1, M2, M*, in such a way as to capture what M said) there seems to be a right order to do the evaluation in. First you figure out whether the normal believer or the normal skeptic is right about all the other statements in the book, then you count the assurance as false only if that’s entailed by the falsity of one of the other conjuncts. And that’s how you get the truth-value of M.
You could say, “O.K., well, that gives us a convention for calling M true or false and so also a convention for calling T true or false.” But of course if that is the convention, then we don’t have one for T, since T doesn’t have any “conjuncts” besides itself. There doesn’t seem to be any point at all at which it could be tied down to anything in logical space. So it does seem to me that there has to be an important difference between M and T; the question is how to spell out what that difference is.
As for the suggestion that we can translate M simply as M2, and so get the truth-conditions that we want, well, I agree that we can, but I’m not at all sympathetic to the claim that that’s how we should understand what Polo said. Because, well, that’s not what Polo said, and there are also technical problems that surface in most of the accounts that would give you some motivation for making the translation. I don’t know about you, but it certainly seems true to me that if Polo lied when he said, “This book contains nothing but the truth,” then his book contains at least two counterexamples to his claim: first, whatever it was he was lying about as far as his journey is concerned, and second, the assurance that he was telling the truth.