by Aristotle
Moreover, a man should make the problem into a proposition for himself, and [10] then bring an objection against it; for the objection will be a ground of attack upon the thesis. This rule is very nearly the same as the rule to look into cases where a predicate has been said to belong to all or none of something; but it differs in the turn of the argument.
Moreover, you should determine what kind of things should be called as most men call them, and what should not. For this is useful both for establishing and for [15] overthrowing a view: e.g. you should say that we ought to use our words to mean the same things as most people mean by them, but when we ask what kinds of things are or are not of such and such a kind, we should not here go with the multitude: e.g. it is right to call healthy whatever tends to produce health, as do most men; but in saying whether the object before us tends to produce health or not, we should adopt the [20] language no longer of the multitude but of the doctor.
3 · Moreover, if a term be used in several ways, and it has been laid down that it belongs or that it does not belong to something, you should prove your case of one of its several uses, if you cannot prove it of both. This rule is to be observed in [25] cases where the difference of use is undetected; for supposing this to be obvious, then the other man will object that the point which he himself questioned has not been discussed, but only the other point. This commonplace rule is convertible for purposes both of establishing and of overthrowing a view. For if we want to establish a statement, we shall prove that in one use the attribute belongs, if we cannot show [30] it of both; whereas if we are overthrowing a statement, we shall prove that in one use the attribute does not belong, if we cannot prove it of both. Of course, in overthrowing a statement there is no need to start the discussion by securing any admission, whether the attribute is said to belong to all or to none of something; for if we prove that in any case whatever the attribute does not belong, we shall have demolished the universal assertion of it, and likewise if we prove that it belongs even [35] in a single case, we shall demolish the universal denial of it. Whereas in establishing a statement we ought to secure a preliminary admission that if it belongs in any case whatever, it belongs universally, supposing this claim to be a plausible one. For it is not enough to argue for a single instance in order to prove that an attribute belongs [110b1] universally; e.g. to argue that if the soul of man is immortal, then every soul is immortal, so that a previous admission must be secured that if any soul whatever is immortal, then every soul is immortal. This is not to be done in every case, but only [5] whenever we are not easily able to quote any single argument applying to all cases in common, as (e.g.) the geometrician can argue that the triangle has its angles equal to two right angles.
If, again, the multiplicity of uses of a term is obvious, distinguish how many uses it has before proceeding either to demolish or to establish: e.g. supposing the [10] right thing to do to be the expedient or the honourable, you should try either to establish or to demolish both of the subject in question; e.g. by showing that it is honourable and expedient, or that it is neither honourable nor expedient. Supposing, however, that it is impossible to show both, you should prove the one, adding an indication that it is true in the one sense and not in the other. The same rule applies [15] also when the number of uses into which it is divided is more than two.
Again, consider those terms whose uses are many, but differ not by way of homonymy, but in some other way: e.g. The science of many things is one: here many things may be the end and the means to that end, as (e.g.) medicine is the science both of producing health and of dieting; or they may be both of them ends, [20] as the science of contraries is said to be the same (for of contraries the one is no more an end than the other); or again they may be an essential and an accidental attribute, as (e.g.) the essential fact that the triangle has its angles equal to two right angles, and the accidental fact that the equilateral figure has them so—for it [25] is because of the accident of the equilateral triangle happening to be a triangle that we know that it has its angles equal to two right angles. If, then, it is not possible in any way that the science of many things should be the same, it clearly is altogether impossible that it should be so; or, if it is possible in some way, then clearly it is [30] possible. Distinguish as many uses as are required: e.g. if we want to establish a view, we should bring forward such uses as admit that view, and should divide them only into those which also are required for the establishment of our case; whereas if we want to overthrow a view, we should bring forward all that do not admit that view, and leave the rest aside. We must proceed thus in this case too when the multiplicity of uses goes unnoticed. Further, that one thing is, or is not, of or for another should be established by means of the same commonplace rules; e.g. that a [35] particular science is of a particular thing, treated either as an end or as a means to its end, or as accidentally connected with it; or again that it is not of or for it in any of the aforesaid ways. The same rule holds true also of desire and all other terms [111a1] that have more than one object. For the desire for something may be the desire for it as an end (e.g. the desire for health) or as a means to an end (e.g. the desire for being doctored), or as a thing desired accidentally, as, in the case of wine, the sweet-toothed person desires it not because it is wine but because it is sweet. For he [5] desires the sweet for itself, and the wine only accidentally; for if it is dry, he no longer desires it. His desire for it is therefore accidental. This rule is useful in dealing with relative terms; for cases of this kind are generally cases of relative terms.
4 · Moreover, it is well to alter a word into one more familiar, e.g. to substitute ‘clear’ for ‘precise’ in describing a conception, and ‘meddling’ for ‘officious’; for when the expression is made more familiar, the thesis becomes easier [10] to attack. This commonplace rule also is available for both purposes alike, both for establishing and for overthrowing a view.
In order to prove that contrary attributes belong to the same thing, look at its genus; e.g. if we want to prove that rightness and wrongness are possible in regard to [15] perception: to perceive is to judge, and it is possible to judge rightly or wrongly; thus in regard to perception as well rightness and wrongness must be possible. In the present instance the demonstration proceeds from the genus and relates to the species; for judging is the genus of perceiving; for the man who perceives judges in a certain way. Again, it may proceed from the species to the genus; for all the [20] attributes that belong to the species belong to the genus as well; e.g. if there is a bad and a good knowledge there is also a bad and a good disposition; for disposition is the genus of knowledge. Now the former commonplace argument is false for purposes of establishing a view, while the second is true. For there is no necessity [25] that all the attributes that belong to the genus should belong also to the species; for animal is winged and quadruped, but not so man. All the attributes, on the other hand, that belong to the species must of necessity belong also to the genus; for if man is good, then animal also is good. On the other hand, for purposes of overthrowing a view, the former argument is true while the latter is false; for all the [30] attributes which do not belong to the genus do not belong to the species either; whereas all those that are wanting to the species are not of necessity wanting to the genus.
Since those things of which the genus is predicated must also of necessity have one of its species predicated of them, and since those things that are possessed of the genus in question, or are described by terms derived from that genus, must also of [35] necessity be possessed of one of its species or be described by terms derived from one of its species (e.g. if knowledge is predicated of something, then so too will be grammatical or musical knowledge, or knowledge of one of the other sciences; and if any one possesses knowledge or is described by a term derived from knowledge, then [111b1] he will also possess grammatical or musical knowledge or knowledge of one of the other sciences, or will be described by a term derived from one of them, e.g. as a grammarian or a musician)—th
erefore if any expression be asserted that is in any way derived from the genus (e.g. that the soul is in motion), look and see whether it [5] is possible for the soul to be moved with any of the species of motion; whether (e.g.) it can grow or be destroyed or come to be, and so forth with all the other species of motion. For if it cannot be moved in any of these ways, clearly it does not move at all. This commonplace rule is common for both purposes, both for overthrowing and for establishing a view; for if the soul moves with one of the species of motion, [10] clearly it does move; while if it does not move with any of the species of motion, clearly it does not move.
If you are not well equipped with an argument against the thesis, look among the definitions, real or apparent, of the thing before you, and if one is not enough, draw upon several. For it will be easier to attack people when committed to a [15] definition. [For an attack is always more easily made on definitions.]6
Moreover, look and see in regard to the thing in question, what is such that if it is the case the thing in question is the case, or what is necessarily the case if the thing in question is the case: if you wish to establish a view inquire what there is such that if it is the case the thing in question will be the case (for if the former be [20] proved to hold, then the thing in question will also have been proved to hold); while if you want to overthrow a view, ask what it is that is the case if the thing in question is the case (for if we show that what follows from the thing in question is not the case, we shall have demolished the thing in question).
Moreover, look at the time involved, to see if there is any discrepancy [25] anywhere: e.g. suppose a man to have stated that what is being nourished of necessity grows; for animals are always being nourished, but they do not always grow. Likewise, also, if he has said that knowing is remembering; for the one is concerned with past time, whereas the other has to do also with the present and the future. For we are said to know things present and future (e.g. that there will be an [30] eclipse), whereas it is impossible to remember anything save what is past.
5 · Moreover, there is the sophistic turn of argument, whereby we draw our opponent into the kind of statement against which we shall be well supplied with lines of argument. This process is sometimes a real necessity, sometimes an apparent necessity, sometimes neither an apparent nor a real necessity. It is really [35] necessary whenever the answerer has denied any view that would be useful in attacking the thesis, and the questioner thereupon addresses his arguments to the support of this view, and when moreover the view in question happens to be one of a kind on which he has a good stock of lines of argument. Likewise, also, it is really necessary whenever starting from the view laid down, he reduces it to something [112a1] else and then tries to demolish that statement; for when this has been demolished, the view originally laid down is demolished as well. It is an apparent necessity, when the point to which the arguments come to be directed appears to be useful, and relevant to the thesis, without being really so; whether it be that the man who is undertaking the argument has refused to concede something, or whether the [5] questioner has reached it by a reputable reduction based upon the thesis and then tries to demolish it. The remaining case is when the point to which the argument comes to be directed is neither really nor apparently necessary, and it turns out that the answer is refuted on an irrelevant issue. You should beware of the last of the [10] aforesaid methods; for it appears to be wholly disconnected from, and foreign to, the art of dialectic. For this reason, moreover, the answerer should not lose his temper, but assent to those statements that are of no use in attacking the thesis, adding an indication whenever he assents although he does not agree with the view. For, for the most part, it increases the confusion of questioners if, after all propositions of [15] this kind have been granted them, they can then draw no conclusion.
Moreover, any one who has made any statement whatever has in a certain sense made several statements, inasmuch as each statement has a number of necessary consequences: e.g. anyone who said that something is a man has also said that it is an animal and that it is animate and a biped and capable of acquiring reason and knowledge, so that by the demolition of any single one of these [20] consequences, of whatever kind, the original statement is demolished as well. But you should beware here of making a change to a more difficult subject; for sometimes the consequence, and sometimes the original thesis, is the easier to demolish.
6 · In regard to subjects which must have one and one only of two predicates, as (e.g.) a man must have either illness or health, supposing we are well supplied as [25] regards the one for arguing its presence or absence, we shall be well equipped as regards the remaining one as well. This rule is convertible for both purposes; for when we have proved that the one attribute belongs, we shall have proved that the remaining one does not belong; while if we prove that the one does not belong, we shall have proved that the remaining one does belong. Clearly then the rule is useful [30] for both purposes.
Moreover, you may attack by reinterpreting a word in respect of its account, with the implication that it is most fitting so to take it rather than in its established meaning: e.g. it is not, as established use has it, the courageous man who is strong-hearted, but rather the man the state of whose heart is strong—just as the man whose arms are strong is strong-armed.7 Likewise also the man whose star is [35] good is well-starred—as Xenocrates says, he who has a noble soul is well-starred. For a man’s star is his soul.
Some things occur of necessity, others for the most part, others however it may [112a1] chance; if therefore what is necessary has been asserted to hold for the most part, or if what holds for the most part (either itself or its contrary) has been stated to hold of necessity, it always gives an opportunity for attack. For if what is necessary has [5] been asserted to hold for the most part, clearly the speaker has denied an attribute to be universal which is universal, and so has made a mistake; and so he has if he has declared what holds for the most part to be necessary; for then he declares it to belong universally when it does not so belong. Likewise also if he has declared the contrary of what holds for the most part to be necessary. For the contrary of what [10] holds for the most part is always a comparatively rare attribute: e.g. if men are for the most part bad, they are comparatively seldom good, so that his mistake is even worse if he has declared them to be good of necessity. The same is true also if he has declared a matter of chance to hold of necessity or for the most part; for a matter of chance holds neither of necessity nor for the most part. If the thing holds for the [15] most part, then even supposing his statement does not distinguish whether he meant that it holds for the most part or that it holds necessarily, it is open to you to discuss it on the assumption that he meant that it holds necessarily: e.g. if he has stated without any distinction that disinherited persons are bad, you may assume in discussing it that he means that they are so necessarily. [20]
Moreover, look and see also if he has stated a thing to be an accident of itself, taking it to be a different thing because it has a different name, as Prodicus used to divide pleasures into joy and delight and good cheer; for all these are names of the same thing, to wit, pleasure. If then any one says that joyfulness is an accidental [25] attribute of cheerfulness, he would be declaring it to be an accidental attribute of itself.
7 · Inasmuch as contraries can be conjoined with each other in six ways, and four of these conjunctions constitute a contrariety, we must take hold of contraries in whatever way they may be of use both in demolishing and in establishing a view. [30] Well then, that the modes of conjunction are six is clear; for either each of the one pair of contraries will be conjoined to each of the other; and this gives two modes, e.g. to do good to friends and to do evil to enemies, or per contra to do evil to friends and to do good to enemies. Or else both of the first pair may be attached to one of [35] the second; and this too gives two modes, e.g. to do good to friends and to do evil to friends, or to do good to enemies and to do evil to enemies. Or one of the first pair may be at
tached to both of the second; and this also gives two modes, e.g. to do good to friends and to do good to enemies, or to do evil to friends and evil to enemies.
[113a1] The first two then of the aforesaid conjunctions do not constitute any contrariety; for the doing of good to friends is not contrary to the doing of evil to enemies; for both courses are desirable and belong to the same disposition. Nor is the doing of evil to friends contrary to the doing of good to enemies; for both of these [5] are objectionable and belong to the same disposition; and one objectionable thing is not thought to be the contrary of another, unless the one refers to an excess, and the other to a defect—for an excess is thought to belong to the class of objectionable things, and likewise also a defect. But the other four all constitute a contrariety. For [10] to do good to friends is contrary to the doing of evil to friends; for it proceeds from the contrary disposition, and the one is desirable, and the other objectionable. The case is the same also in regard to the other conjunctions; for in each combination the one course is desirable, and the other objectionable, and the one belongs to an honourable disposition and the other to a bad. Clearly, then, from what has been [15] said, the same thing has more than one contrary. For the doing of good to friends has as its contrary both the doing of good to enemies and the doing of evil to friends. Likewise, if we examine them in the same way, we shall find that the contraries of each of the others also are two in number. Select therefore whichever of the two contraries is useful in attacking the thesis.
[20] Moreover, if the accident of a thing has a contrary, see whether it belongs to the subject to which the accident in question has been declared to belong; for if the latter belongs the former could not belong; for it is impossible that contrary predicates should belong at the same time to the same thing.
Or again, look and see if anything has been said about something, of such a [25] kind that if it is true, contrary predicates must necessarily belong to the thing; e.g. if he has said that the Ideas exist in us. For then the result will be that they are both in motion and at rest, and moreover that they are objects both of sensation and of thought. For according to those who posit the existence of Ideas, those Ideas are at rest and are objects of thought; while if they exist in us, it is impossible that they should be unmoved; for when we move, it follows necessarily that all that is in us [30] moves with us as well. Clearly also they are objects of sensation, if they exist in us; for it is through the sensation of sight that we recognize the form present in each individual.