6.51 Skepticism is not irrefutable, but rather manifestly nonsensical [offenbar unsinnig], if it would doubt where nothing can be asked.
Since doubt can only exist where a question exists; a question only where an answer exists, and this only where something can be said.
The ‘if’ might be worth noting here. Wondering about the meaning of life would then be manifestly nonsensical too. Cf. Kant’s Critique of Pure Reason: “To know what questions may reasonably be asked is already a great and necessary proof of sagacity and insight. For if a question is absurd in itself and calls for an answer where none is required, it not only brings shame on the propounder of the question, but may betray an incautious listener into absurd answers, thus presenting, as the ancients said, the ludicrous spectacle of one man milking a he-goat and the other holding a sieve underneath.” (A 58/B 82-83)