If human nature were not base, but thoroughly honourable, we should in every debate have no other aim than the discovery of truth; we should not in the least care whether the truth proved to be in favour of the opinion which we had begun by expressing, or of the opinion of our adversary. That we should regard as a matter of no moment, or, at any rate, of very secondary consequence; but, as things are, it is the main concern. Our innate vanity, which is particularly sensitive in reference to our intellectual powers, will not suffer us to allow that our first position was wrong and our adversary’s right. The way out of this difficulty would be simply to take the trouble always to form a correct judgment. For this a man would have to think before he spoke. But, with most men, innate vanity is accompanied by loquacity and innate dishonesty. They speak before they think; and even though they may afterwards perceive that they are wrong, and that what they assert is false, they want it to seem thecontrary. The interest in truth, which may be presumed to have been their only motive when they stated the proposition alleged to be true, now gives way to the interests of vanity: and so, for the sake of vanity, what is true must seem false, and what is false must seem true.
Arthur Schopenhauer, The Art of Always Being Right
dishonesty, falsehood, truth, vanity