"But how do you know that naturalism is true? That you believe it with great conviction cuts no ice. As Nietzsche says, in his typically exaggerated and febrile way, "Convictions are the greatest enemies of truth." Can you prove naturalism? If you try, you will soon entangle yourself in a thicket of thorny metaphysical questions from which you will not escape unbloodied. You cannot prove it. I guarantee it."