V
To prove the truth of a proposition, you may also employ previous propositions that are not true, should your opponent refuse to admit the true ones, either because he fails to perceive their truth, or because he sees that the thesis immediately follows from them. In that case the plan is to take propositions which are false in themselves but true for your opponent, and argue from the way in which he thinks, that is to say, ex concessis. For a true conclusion may follow from false premisses, but not vice versâ. In the same fashion your opponent's false propositions may be refuted by other false propositions, which he, however, takes to be true; for it is with him that you have to do, and you must use the thoughts that he uses. For instance, if he is a member of some sect to which you do not belong, you may employ the declared, opinions of this sect against him, as principles.11
VI
Another plan is to beg the question in disguise by postulating what has to be proved, either (1) under another name; for instance, "good repute" instead of "honour"; "virtue" instead of "virginity," etc.; or by using such convertible terms as "red-blooded animals" and "vertebrates"; or (2) by making a general assumption covering the particular point in dispute; for instance, maintaining the uncertainty of medicine by postulating the uncertainty of all human knowledge. (3) If, vice versâ, two things follow one from the other, and one is to be proved, you may postulate the other. (4) If a general proposition is to be proved, you may get your opponent to admit every one of the particulars. This is the converse of the second.12
VII
Should the disputation be conducted on somewhat strict and formal lines, and there be a desire to arrive at a very clear understanding, he who states the proposition and wants to prove it may proceed against his opponent by question, in order to show the truth of the statement from his admissions. The erotematic, or Socratic, method was especially in use among the ancients; and this and some of the tricks following later on are akin to it.13
The plan is to ask a great many wide-reaching questions at once, so as to hide what you want to get admitted, and, on the other hand, quickly propound the argument resulting from the admissions; for those who are slow of understanding cannot follow accurately, and do not notice any mistakes or gaps there may be in the demonstration.
VIII
This trick consists in making your opponent angry; for when he is angry he is incapable of judging aright, and perceiving where his advantage lies. You can make him angry by doing him repeated injustice, or practising some kind of chicanery, and being generally insolent.
IX
Or you may put questions in an order different from that which the conclusion to be drawn from them requires, and transpose them, so as not to let him know at what you are aiming. He can then take no precautions. You may also use his answers for different or even opposite conclusions, according to their character. This is akin to the trick of masking your procedure.
X
If you observe that your opponent designedly returns a negative answer to the questions which, for the sake of your proposition, you want him to answer in the affirmative, you must ask the converse of the proposition, as though it were that which you were anxious to see affirmed; or, at any rate, you may give him his choice of both, so that he may not perceive which of them you are asking him to affirm.
XL
If you make an induction, and your opponent grants you the particular cases by which it is to be supported, you must refrain from asking him if he also admits the general truth which issues from the particulars, but introduce it afterwards as a settled and admitted fact; for, in the meanwhile, he will himself come to believe that he has admitted it, and the same impression will be received by the audience, because they will remember the many questions as to the particulars, and suppose that they must, of course, have attained their end.
XII
If the conversation turns upon some general conception which has no particular name, but requires some figurative or metaphorical designation, you must begin by choosing a metaphor that is favourable to your proposition. For instance, the names used to denote the two political parties in Spain, Serviles and Liberates, are obviously chosen by the latter. The name Protestants is chosen by themselves, and also the name Evangelicals; but the Catholics call them heretics. Similarly, in regard to the names of things which admit of a more exact and definite meaning: for example, if your opponent proposes an alteration, you can call it an innovation, as this is an invidious word. If you yourself make the proposal, it will be the converse. In the first case, you can call the antagonistic principle "the existing order," in the second, "antiquated prejudice." What an impartial man with no further purpose to serve would call "public worship" or a "system of religion," is described by an adherent as "piety," "godliness": and by an opponent as "bigotry," "superstition." This is, at bottom, a subtle petitio principii. What is sought to be proved is, first of all, inserted in the definition, whence it is then taken by mere analysis. What one man calls "placing in safe custody," another calls "throwing into prison." A speaker often betrays his purpose beforehand by the names which he gives to things. One man talks of "the clergy"; another, of "the priests."
Of all the tricks of controversy, this is the most frequent, and it is used instinctively. You hear of "religious zeal," or "fanaticism"; a "faux pas" a "piece of gallantry," or "adultery"; an "equivocal," or a "bawdy" story; "embarrassment," or "bankruptcy"; "through influence and connection," or by "bribery and nepotism"; "sincere gratitude," or "good pay."
XIII
To make your opponent accept a proposition, you must give him the counter-proposition as well, leaving him his choice of the two; and you must render the contrast as glaring as you can, so that to avoid being paradoxical he will accept the proposition, which is thus made to look quite probable. For instance, if you want to make him admit that a boy must do everything that his father tells him to do, ask him "whether in all things we must obey or disobey our parents." Or, if a thing is said to occur "often," ask whether by "often" you are to understand few or many cases; and he will say "many." It is as though you were to put grey next black, and call it white; or next white, and call it black.
XIV
This, which is an impudent trick, is played as follows: When your opponent has answered several of your questions without the answers turning out favourable to the conclusion at which you are aiming, advance the desired conclusion, although it does not in the least follow, as though it had been proved, and proclaim it in a tone of triumph. If your opponent is shy or stupid, and you yourself possess a great deal of impudence and a good voice, the trick may easily succeed. It is akin to the fallacy non causae ut causae.
XV
If you have advanced a paradoxical proposition and find a difficulty in proving it, you may submit for your opponent's acceptance or rejection some true proposition, the truth of which, however, is not quite palpable, as though you wished to draw your proof from it. Should he reject it because he suspects a trick, you can obtain your triumph by showing how absurd he is; should he accept it> you have got reason on your side for the moment, and must now look about you; or else you can employ the previous trick as well, and maintain that your paradox is proved by the proposition which he has accepted. For this an extreme degree of impudence is required; but experience shows cases of it, and there are people who practise it by instinct.