Davidson's presumable claim against the brain in a vat in 1983(oh, i was born) is not useful alone. "The causality plays an indispensable role in determining the content of what we say and believe" so what the brain said would be interpreted as "Vatese", not English, and we don't have to apply to the Vatese words the criteria that are for determining the truth value of English words.

At least solipsists and idealists wouldn't be threatened at all by this line.

What matters is in fact here is not a blog site. i may need some kind of interactive factors, of course i don't take this problem as serious, though.