All great deceivers proceed in a way that is worth noting, for to this they owe their power. In the actual act of deceit, among all the preparations, the awe-inspiring features of their voice, expression, gestures, amid scenery contrived for effect, the belief in themselves comes over them: this is the one who then speaks so wondrously and so authoritatively to the surrounding people.
The founders of religions differ from those great deceivers in that they do not emerge from this state of self-delusion: or they have only on very rare occasions those clearer moments when doubt overpowers them; but they generally comfort themselves by imputing these clearer moments to the evil antagonist. Self-deception must be present for these individuals, as well as those, to bring to about their great effects. For human beings believe in the truth of what is quite manifestly strongly believed. – from Frederich Nietzsche’s Human, All Too Human I (40, 52)