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 versa_. 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.[1]

[Footnote 1: Aristotle, _Topica_ bk. viii., chap. 2.]

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 a.s.sumption covering the particular point in dispute; for instance, maintaining the uncertainty of medicine by postulating the uncertainty of all human knowledge. (3) If, _vice versa_, 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.[1]

[Footnote 1: _Idem_, chap. 11. The last chapter of this work contains some good rules for the practice of Dialectics.]

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.[1]

[Footnote 1: They are all a free version of chap. 15 of Aristotle's _De Sophistici Elenchis_.]

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," "G.o.dliness": and by an opponent as "bigotry," "superst.i.tion."

This is, at bottom, a subtle _pet.i.tio principii_. What is sought to be proved is, first of all, inserted in the definition, whence it is then taken by mere a.n.a.lysis. 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; "embarra.s.sment," or "bankruptcy"; "through influence and connection," or by "bribery and nepotism"; "sincere grat.i.tude," 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.

XVI.

Another trick is to use arguments _ad hominem_, or _ex concessis_[1]

When your opponent makes a proposition, you must try to see whether it is not in some way--if needs be, only apparently--inconsistent with some other proposition which he has made or admitted, or with the principles of a school or sect which he has commended and approved, or with the actions of those who support the sect, or else of those who give it only an apparent and spurious support, or with his own actions or want of action. For example, should he defend suicide, you may at once exclaim, "Why don't you hang yourself?" Should he maintain that Berlin is an unpleasant place to live in, you may say, "Why don't you leave by the first train?" Some such claptrap is always possible.

[Footnote 1: The truth from which I draw my proof may he either (1) of an objective and universally valid character; in that case my proof is veracious, _secundum veritatem_; and it is such proof alone that has any genuine validity. Or (2) it may be valid only for the person to whom I wish to prove my proposition, and with whom I am disputing. He has, that is to say, either taken up some position once for all as a prejudice, or hastily admitted it in the course of the dispute; and on this I ground my proof. In that case, it is a proof valid only for this particular man, _ad kominem. I_ compel my opponent to grant my proposition, but I fail to establish it as a truth of universal validity. My proof avails for my opponent alone, but for no one else.

For example, if my opponent is a devotee of Kant's, and I ground my proof on some utterance of that philosopher, it is a proof which in itself is only _ad hominem_. If he is a Mohammedan, I may prove my point by reference to a pa.s.sage in the Koran, and that is sufficient for him; but here it is only a proof _ad hominem_,]

XVII.

If your opponent presses you with a counter-proof, you will often be able to save yourself by advancing some subtle distinction, which, it is true, had not previously occurred to you; that is, if the matter admits of a double application, or of being taken in any ambiguous sense.

XVIII.

If you observe that your opponent has taken up a line of argument which will end in your defeat, you must not allow him to carry it to its conclusion, but interrupt the course of the dispute in time, or break it off altogether, or lead him away from the subject, and bring him to others. In short, you must effect the trick which will be noticed later on, the _mutatio controversiae_. (See -- xxix.)

XIX.

Should your opponent expressly challenge you to produce any objection to some definite point in his argument, and you have nothing much to say, you must try to give the matter a general turn, and then talk against that. If you are called upon to say why a particular physical hypothesis cannot be accepted, you may speak of the fallibility of human knowledge, and give various ill.u.s.trations of it.

XX.

When you have elicited all your premisses, and your opponent has admitted them, you must refrain from asking him for the conclusion, but draw it at once for yourself; nay, even though one or other of the premisses should be lacking, you may take it as though it too had been admitted, and draw the conclusion. This trick is an application of the fallacy _non causae ut causae_.

XXI.

When your opponent uses a merely superficial or sophistical argument and you see through it, you can, it is true, refute it by setting forth its captious and superficial character; but it is better to meet him with a counter-argument which is just as superficial and sophistical, and so dispose of him; for it is with victory that you are concerned, and not with truth. If, for example, he adopts an _argumentum ad hominem_, it is sufficient to take the force out of it by a counter _argumentum ad hominem_ or _argumentum ex concessis_; and, in general, instead of setting forth the true state of the case at equal length, it is shorter to take this course if it lies open to you.