"For human nature is such that if A. and B. are engaged in thinking in common, and are communicating their opinions to one another on any subject, so long as it is not a mere fact of history, and A. perceives that B.‘s thoughts on one and the same subject are not the same as his own, he does not begin by revising his own process of thinking, so as to discover any mistake which he may have made, but he assumes that the mistake has occurred in B.‘s. In other words, man is naturally obstinate; and this quality in him is attended with certain results, treated of in the branch of knowledge which I should like to call Dialectic, but which, in order to avoid misunderstanding, I shall call Controversial or Eristical Dialectic. Accordingly, it is the branch of knowledge which treats of the obstinacy natural to man. Eristic is only a harsher name for the same thing.

Controversial Dialectic is the art of disputing, and of disputing in such a way as to hold one’s own, whether one is in the right or the wrong—per fas et nefas.3 A man may be objectively in the right, and nevertheless in the eyes of bystanders, and sometimes in his own, he may come off worst. For example, I may advance a proof of some assertion, and my adversary may refute the proof, and thus appear to have refuted the assertion, for which there may, nevertheless, be other proofs. In this case, of course, my adversary and I change places: he comes off best, although, as a matter of fact, he is in the wrong."
- Arthur Schopenhauer, The Art of Controversy