"…is there any actual difference between a lie and a conviction? The entire world believes there is; but what doesn’t the world believe! Every conviction has its history, its primitive forms, its stage of tentativeness and error: it becomes a conviction only after having been, for a long time, not one, and then, for an even longer time, hardly one.
What if falsehood is also one of these embryonic forms of conviction? Sometimes all that is needed is a change in persons: what was a lie in the father becomes a conviction in the son. I call it lying to refuse to see what one sees, or to refuse to see it as it is: whether the lie is spoken before witnesses or not spoken before witnesses doesn’t matter.
The most common sort of lie is one in which someone deceives him or herself: the deception of others is a relatively rare offense. Now, this determination not to see what one sees, this determination not to see it as it is, is almost the first requirement for all who belong to a party of whatever sort: the party man inevitably becomes a liar."
From Friedrich Wilhelm Nietzsche, The Anti-Christ, 1888