"He does not seem to know what an argument is. He never uses arguments himself. He never troubles himself to answer the arguments of his opponents. It has never occurred to him, that a man ought to be able to give some better account of the way in which he has arrived at his opinions than merely that it is his will and pleasure to hold them. It has never occurred to him that there is a difference between assertion and demonstration, that a rumour does not always prove a fact, that a single fact, when proved, is hardly foundation enough for a theory, that two contradictory propositions cannot be undeniable truths, that to beg the question is not the way to settle it, or that when an objection is raised, it ought to be met with something more convincing than 'scoundrel' and 'blockhead'." (Macaulay.)

"[The greatest orator always studies] his adversary's case with as great, if not still greater, intensity than even his own. ... He who knows only his own side of the case, knows little of that. His reasons may be good, and no one may have been able to refute them. But if he is equally unable to refute the reasons on the opposite side [then he may not be able to convince himself or another of the truth of the matter.] ... Nor is it enough that he should hear the arguments of adversaries from his own teachers, presented as they state them, and accompanied by what they offer as refutations. That is not the way to do justice to the arguments, or bring them into real contact with his own mind. He must be able to hear them from persons who actually believe them; who defend them in earnest, and do their very utmost for them. He must know them in their most plausible and persuasive form; he must feel the whole force of the difficulty which the true view of the subject has to encounter and dispose of; else he will never really possess himself of the portion of truth which meets and removes that difficulty. Ninety-nine in a hundred of what are called educated men are in this condition; even of those who can argue fluently for their opinions. Their conclusion may be true, but it might be false for anything they know: they have never thrown themselves into the mental position of those who think differently from them, and considered what such persons may have to say; and consequently they do not, in any proper sense of the word, know the doctrine which they themselves profess. They do not know those parts of it which explain and justify the remainder; the considerations which show that a fact which seemingly conflicts with another is reconcilable with it, or that, of two apparently strong reasons, one and not the other ought to be preferred. All that part of the truth which turns the scale, and decides the judgment of a completely informed mind, they are strangers to; nor is it ever really known, but to those who have attended equally and impartially to both sides, and endeavoured to see the reasons of both in the strongest light." (Mill, On Liberty.)