Hmm. I was going to say "assign it the value of true, and it returns true. Assign it the value of false, and it returns a contradiction", but on reflection that's not the case. If you assign it the value of false, then the claim becomes ¬(A is true), so it returns false.

So I was wrong - the proposition is a null proposition, it simply returns the truth value you assign to it. I don't know if ambiguous is the best way to describe it, but 'true' certainly isn't.

edit: perhaps cata's 'trivial' is a good word for it.

Interesting. If I infer correctly...

Tordmor messed up and wrote "This proposition is true" when he probably would have wanted to have referred to "This proposition is false".

Shokwave correctly notes that "This proposition is true" isn't ambiguous at all, it essentially returns the value True.

Jonii also correctly observes that the person speaking the claim "This proposition is true" could be lying or mistaken (to the extent that the statement has bearing on facts external to the phrase). Apparent disagreement with Shokwave is likely to be due to ambiguity in the casual English representations of logical dereferencing.