You can say a true sentence that sounds absurd the moment you say it about yourself

G.E. Moore noticed something odd about statements like 'It's raining, but I don't believe it's raining.' The sentence can be true — it might genuinely be raining while you genuinely don't believe it — yet saying it aloud about your own belief sounds almost unsayable, a self-undermining absurdity pure logic alone can't explain. Wittgenstein called it one of the most interesting puzzles Moore ever raised, since it exposes a gap between what makes a statement true and what makes it assertable.

— G.E. Moore, A Reply to My Critics — In The Philosophy of G.E. Moore, ed. P.A. Schilpp, 1942