Alternatively, he could lock himself onto a sun-destroying path, and then forcibly do an unBayesian update away from the existence of the sun.
Alternately, he could interpret the sentence literally, note that ‘not at all’ is a level of insistence, deny the existence of the sun not at all, and then destroy it.
You’re going to have trouble destroying the Sun if you don’t believe it exists.
He only has to deny that it exists.
Alternatively, he could lock himself onto a sun-destroying path, and then forcibly do an unBayesian update away from the existence of the sun.
Alternately, he could interpret the sentence literally, note that ‘not at all’ is a level of insistence, deny the existence of the sun not at all, and then destroy it.