Book 1
Chap. 1. Of the Argument of this Treatise: of Syllogism and its kinds.
Chap. 2. That this Treatise is useful for three purposes.
Chap. 3. In what consists Dialectical Skill.
Chap. 4. Of Problem and Proposition.
Chap. 5. Of Definition, Genus, Property, and Accident.
Chap. 6. Of Arguments against Genus, etc., as applicable to the Subversion of Definition.
Chap. 7. In how many ways "Same" (τὸ ταὐτὸν) is predicated.
Chap. 8. That it may be proved by Induction and Syllogism that all questions appertain to Definition, Genus, Property, or Accident.
Chap. 9. Upon the Genera of the Categories.
Chap. 10. Of the Dialectic Proposition.
Chap. 11. Of the Dialectical Problem, and of Thesis.
Chap. 12. Of Syllogism and Induction.
Chap. 13. Of the Means adapted to the Provision of Syllogisms and Inductions.
Chap. 14. Upon the Selection of Propositions.
Chap. 15. Of the Knowledge of Diverse Modes of Predication.
Chap. 16. Upon the Discovery of Differences.
Chap. 17. How similitude is to be observed in things of different genera, and in the same genus.
Chap. 18. On the Utility of these Inquiries in Disputation.
Book 2
Chap. 1. Of the Division of Problems: of the Conversion of the Accidental: and of Problematical Errors.
Chap. 2. Of the "Places," belonging to Problems of Accident.
Chap. 3. Of the Topics belonging to Multifarious Predication.
Chap. 4. Topics relative to Name, Genus, Species, Definition, Time.
Chap. 5. Upon drawing on the Adversary to our own strong points: Subversion of the Proposition by that of the Consequent.
Chap. 6. Of Topics connected with Affirmative and Negative Argument relatively, etc.
Chap. 7. On Places connected with Contraries.
Chap. 8. Of Topics, from the sequence of Opposition.
Chap. 9. Topics of Co-ordinates, Generation and Corruption.
Chap. 10. As to Similars, the more and less.
Chap. 11. Of Arguments from Addition (ἐκ τῆς προθέσεως) and the Simple (τὸ ἁπλῶς).
Book 3
Chap. 1. Of Topics relative to the More Eligible and Better.
Chap. 2. Upon the Similar and Super-excellent.
Chap. 3. Of the more Eligible, continued.
Chap. 4. Of the Use of these Places for Demonstrating what is Eligible or to be Avoided (τὸ αἱρετὸν ἤ φευκτόν).
Chap. 5. Of Topics pre-eminently Universal from the more and greater.
Chap. 6. That the above Places are useful for Particular Problems.
Book 4
Chap. 1. Of Topics relative to Genus.
Chap. 2. Of Topics relative to Genus, Species, and Difference.
Chap. 3. Of the proper Constitution of Genus and Species.
Chap. 4. Of Topics belonging to Similitude, Relatives, etc.
Chap. 5. Topics relative to Genus continued.
Chap. 6. Of Topics relative to Genus, continued.
Book 5
Chap. 1. Upon Property.
Chap. 2. Of the correct Exposition of the Property.
Chap. 3. Topics connected with Property continued.
Chap. 4. Topics relative to the Question, whether the assigned be Property or not.
Chap. 5. The same Subject continued.
Chap. 6. Of Property from Opposites.
Chap. 7. Of Property as to Cases.
Chap. 8. Of Property from the More and Less.
Chap. 9. Topics upon Property as to Capacity, etc.
Book 6
Chap. 1. On Places connected with Definition.
Chap. 2. Of Places relative to defining rightly.
Chap. 3. Of Superfluity in Definition.
Chap. 4. As to whether the Definition contains what a thing is.
Chap. 5. Topics connected with Definition, as to Genus.
Chap. 6. Of Difference, as to Genus, Species, etc.
Chap. 7. Whether another Definition may be more explicit, etc.
Chap. 8. Of Definition as to Relation.
Chap. 9. Of Definition as to Contraries, etc.
Chap. 10. As to the similarity of cases in the Definition and in the Noun.
Chap. 11. Of Composite and Singular Definition.
Chap. 12. The same subject continued.
Chap. 13. Of Distinctive Notions in Definition.
Chap. 14. On the Definition of the whole as a Composite, etc.
Book 7
Chap. 1. Of the Question whether a Thing be the same or different.
Chap. 2. Distinction between Confirmative and Subversive Places of Definition.
Chap. 3. Of Topics suitable to confirming Definition.
Chap. 4. That the Places already mentioned, are the most appropriate of all.
Chap. 5. Of Confirmation and Subversion of Definition.
Book 8
Chap. 1. Of the Order of Argument.
Chap. 2. Other Topics relative to Dialectic Interrogation.
Chap. 3. Of Dialectic Argument generally.
Chap. 4. Of Dialectic Responsion.
Chap. 5. Various Objects in Disputation of the Thesis, etc.
Chap. 6. Certain Rules as to Admissible Points.
Chap. 7. The Practice of the Respondent in cases of Ambiguity.
Chap. 8. Of Responsion to Induction.
Chap. 9. Of the Defence of the Thesis.
Chap. 10. Of the Solution of False Arguments, and of the Methods of preventing the Conclusion.
Chap. 11. Of the Reprehension of Argument.
Chap. 12. Of Evident and False Reasoning.
Chap. 13. Of Petitio Principii, and Contraries.
Chap. 14. Of Dialectic Exercise.
The purpose of this treatise is to discover a method by which we shall be able to syllogize about every proposed problem from probabilities, and when we ourselves sustain the argument we may assert nothing repugnant. First, then, we must declare what a syllogism is and what are its differences, in order that the dialectic syllogism may be apprehended, for we investigate this in the proposed treatise.
A syllogism then is a discourse in which, certain things being laid down, something different from the posita happens from necessity through the things laid down. Demonstration indeed is when a syllogism consists of things true and primary, or of such a kind as assume the principle of the knowledge concerning them through certain things primary and true; but the dialectic syllogism is that which is collected from probabilities. Things true and primary indeed are those which obtain belief, not through others, but through themselves, as there is no necessity to investigate the "why" in scientific principles, but each principle itself ought to be credible by itself. Probabilities however are those which appear to all, or to most men, or to the wise, and to these either to all or to the greater number, or to such as are especially renowned and illustrious. Moreover a contentious syllogism is one which is constructed from apparent, but not real probabilities, and which appears to consist of probabilities, or of apparent probabilities. For not every thing which appears probable is so, since none of those which are called probable has entirely the superficial image (of probability), as happens to be the case about the principles of contentious arguments, since immediately, and for the most part, the nature of the false in them is evident even to those who have small perception. Let then the first of the syllogisms called contentious, be also called a syllogism, but let the other be a contentious syllogism, yet not a syllogism (simply), since it appears indeed to draw an inference, but does not collect one.
Besides all the above-named syllogisms, there are paralogisms, which consist of things peculiar to certain sciences, as happens to be the case in geometry, and those (sciences) allied to it. For this mode seems to differ from the syllogisms enumerated, since he who describes falsely, neither syllogizes from the true and primary, nor from the probable, for he does not fall into definition, since he neither assumes things which appear to all men, nor those which appear to the greater number, nor to the wise, and to these neither to all, nor to the greater part, nor to the most famous; but he makes a syllogism from assumptions, appropriate indeed to science, yet not from the true, as either by describing semicircles not as they ought to be, or by drawing certain lines not as they ought to be drawn, he produces a paralogism.
Let then the species of syllogisms, to comprehend them summarily, be those which I have stated, and in a word, to sum up all that have been spoken of, and those which shall be mentioned hereafter, let our definition be so far given, because we do not propose to deliver an accurate description of any of these, but wish merely to run through them briefly, thinking it quite sufficient according to the proposed method, in some way or other to be able to know each of them.
It will be consequent upon what we have stated to describe to what an extent and for what subjects this treatise is useful. It is so for three: exercise, conversation, philosophical science. That it is useful for exercise, appears evident from these, that possessing method, we shall be able more easily to argue upon every proposed subject. But for conversation (it is useful), because having enumerated the opinions of the many, we shall converse with them, not from foreign, but from appropriate dogmas, confuting whatever they appear to us to have erroneously stated. Again, (it is useful) for philosophical science, because being able to dispute on both sides, we shall more easily perceive in each the true and the false; also, (it is applicable) to the first principles of each science, since we cannot say any thing about these from the appropriate principles of a proposed science, as they are the first principles of all, but we must necessarily discuss these through probabilities in the singulars. This however is peculiar, or especially appropriate to dialectic, for being investigative, it possesses the way to the principles of all methods.
We shall possess this method perfectly when we are similarly disposed, as in rhetoric, medicine, and such like powers; and this is to effect what we choose from possibilities, since neither will the rhetorician persuade from every mode, nor the physician heal, but if a man omits no possibility we say that he sufficiently possesses science.
First then let us examine of what this method consists. If therefore we assume for how many, what kind of, and from what things, arguments are constructed, and how we may be well provided with these, we shall sufficiently gain our point. Now those things are equal and the same in number from which arguments are constructed, and about which syllogisms are conversant; for arguments are constructed of propositions, but the things with which syllogisms are conversant are problems. Now every proposition and every problem shows either genus, property, or accident; for difference, being generic, we must place together with genus. Since however of property, one kind signifies the very nature of a thing, but the other does not signify it, let property be divided into the two above-named parts, and let what signifies the very nature of a thing be called definition, but let the other, according to the common appellation attributed about these, be called property. Now it is clear from what we have said, that according to the present division it happens that all are four, either property, or definition, or genus, or accident. Let however no one suppose that we say that each of these asserted by itself is a proposition or a problem, but that problems and propositions are produced from these. Still a problem and a proposition differ in mode, since when it is thus said, is a pedestrian biped animal the definition of man? and is animal the genus of man? there is a proposition, but if (it should be said), whether is a pedestrian biped animal the definition of man or not? there is a problem. So also in other things. Wherefore with propriety problems and propositions are equal in number, for from every proposition you will make a problem by changing the mode.
We must describe what definition, property, genus, and accident are. Now definition is a sentence signifying what a thing is: and either a sentence is employed instead of a noun, or a sentence instead of a sentence, since it is possible to define some things which are signified by a sentence. As many however as in some way or other make the explanation by a noun, evidently do not explain the definition of the thing, since every definition is a certain sentence. Still we must refer a thing of this kind to definition, as that the becoming is beautiful; in like manner also whether sense and science are the same or different, since about these definitions, whether they are the same or different, there is a very great discussion. In short, however, all things may be called definitive which are under the same method with definitions, but that all which have been spoken of are of this kind is evident from these (considerations). For when we are able to argue that a thing is the same and that it is different, we shall by the same manner be well supplied with arguments about definitions, since when we have shown that it is not the same we shall have upset the definition. Still what is now said is not converted, since it is not enough to construct a definition to show that it is the same, but for the subversion of definition it is sufficient to show that it is not the same thing.
Property, indeed, is that which does not show what a thing is, but is present to it alone, and reciprocates with the thing. As it is the properly of a man to be capable of grammar, for if he is a man he is capable of grammar, and if he is capable of grammar he is a man; since no one calls property that which may possibly be present with something else, as sleep to a man, not even if it should happen at a certain time to be present with him alone. If then any thing of this kind should be called property, it will not be called property simply, but at a certain time or with reference to something, since to be on the right hand is sometimes a property, but biped happens to be called property with reference to something, as to man with reference to horse and dog; but that nothing which may possibly be present with something else is reciprocally predicated is clear, since it is not necessary if any thing sleeps that it should be a man.
Genus, however, is that which is predicated of many things differing in species, in (answer to) what a thing is; but let those things be said to be predicated in (answer to) what a thing is, which are fitted to answer the person inquiring what the proposed thing is, as it is adapted to man, when it is asked what the proposed thing is, to say that he is animal. Moreover it is generic, whether one thing is in the same genus with another or in a different genus, since such a thing falls under the same method with genus, as having discussed that animal is the genus of man, and in like manner of ox, we shall reason that they are in the same genus; if, however, we should show that it is the genus of one of them, but not of the other, we shall reason that these are not in the same genus.
Accident, again, is that which is not any of these, neither definition, nor property, nor genus; yet it is present with a thing, and is that which may possibly be present with some one and the same thing and may not be present, as, to sit may be and may not be present with some one and the same thing, and in like manner whiteness, for there is nothing to prevent the same thing being at one time white and at another not white. Now of these definitions of accident, the second is the better; since when the first is stated, it is necessary in order to understand it, to know previously what definition genus and property are, but the second is self-sufficient for the knowledge per se of what the thing asserted is. To accident also let comparisons of things with each other belong, in whatever way they are derived from accident, as, whether the honourable or the advantageous be preferable, and whether a life of virtue or of enjoyment is the sweeter, and if there happens to be any other assertion similar to these, for in all things of this kind, the question arises as to which the predicate rather happens to belong. Still from these it is manifest that there is nothing to prevent accident sometimes, and with reference to something, becoming property, as to sit being accident, when some one alone sits, will then be a property, but one not sitting alone, it will be a property with reference to those who do not sit, so that nothing prevents accident from becoming property in a certain relation and at a certain time; simply, however, it will not be property.
Nevertheless we must not forget that every thing which is referred to property, genus, and accident will also be adapted to definitions, for by showing that a thing is not present with that alone which is under definition, as in the case of property, or that what is given in the definition is not genus, or that some one of those things stated in the definition is not present, which may also be said in accident, we shall have subverted the definition; so that, on account of the reason given before, all those things which have been enumerated will after a certain manner be definitive. Nevertheless we must not on this account look for one method universal in all things, as neither is it easy to discover this, and if it were discovered it would be altogether obscure and useless to the proposed treatise. But a peculiar method being delivered as to each of the defined genera singly, the discussion of the proposition will be easy from those things which are appropriate to each. Wherefore, as we have before said, we must make a rough division, but of the rest we must join those which are especially appropriate to each, denominating them both definitive and generic. What, however, have been set forth have almost been adapted to each.
We must first of all distinguish about "the same," in how many ways it is predicated; but "the same." to speak in general terms, may appear to be divided triply, since we are accustomed to denominate a thing the same, in number, or in species, or in genus; in number indeed when the names are many but the thing one, as a garment and a vestment, but in species when the things being many are without specific difference, as man with man, and horse with horse, for such things are said to be the same in species as are under the same species: in like manner also, those are the same in genus which are under the same genus, as horse with man. Nevertheless, it may seem indeed that water from the same fountain, being called the same, has a certain difference besides the modes enumerated, yet such a thing must be placed at least in the same arrangement with those, which are in some way or other said to be under one species, for all such things appear to be of a kindred nature and similar to each other, since all water is said to be the same in species with all water, because of the possession of a certain similarity; but water from the same fountain differs in nothing else except that the similarity is greater; wherefore we do not separate it from those which some way or other are said to be according to one species. Confessedly, however, that which is one in number, seems especially to be called the same, by all men; still we usually attribute this in many ways, most properly indeed and chiefly, when "same" is attributed in name or definition, as garment to a vestment, and animal pedestrian biped, to man; secondly, when (it is attributed) in property, as what is susceptible of science to man, and what naturally is carried upwards, to fire; thirdly, when from accident, as that which sits or is musical, to Socrates. For all these would signify one thing in number, and that what we have now said is true, a person may especially learn, from those who change appellations; for frequently when we desire to call some one who is sitting, by name, we change (the appellation), when he to whom we give the order, does not happen to understand, as if he would rather understand from accidents, and we desire him to call to us, the person who is sitting or discoursing, evidently considering it the same thing to signify by name and by accident. Let therefore "same" be triply divided, as we have said.
That disputations are composed from the things mentioned before, and through these, and pertain to these, we have the first evidence through induction, since if any one considers each of the propositions and problems, it will appear to have originated either from definition, or from property, or from genus, or from accident. Another evidence however is by syllogism, for it is necessary that every thing which is predicated of a certain thing, should either reciprocate with that thing or not. And if indeed it reciprocates it will be definition or property, since if it signifies what a thing is, it is definition, but if it does not signify it, it is property, for this was property, viz. that which reciprocates indeed, but does not signify what a thing is. If however it does not reciprocate with the thing, it either is one of those which are predicated in the definition of the subject, or it is not, and if it is one of those predicated in the definition it would be genus or difference, since definition consists of genus and differences, but if it is not of those predicated in definition, it would be evidently accident, for that was said to be accident which is neither definition, nor genus, nor property, yet is present with a thing.
We must next define the genera of the Categories, in which the above-named four (differences) are inherent. Now these are tea in number; what a thing is, quantity, quality, relation, where, when, position, possession, action, passion, for accident, and genus, and property, and definition will always be in one of these categories, since all propositions through these signify either what a thing is, or quality, or quantity, or some other category. Moreover, it is evident from these that he who signifies what a thing is, at one time signifies substance, at another quality, and at another some other category. For when man being proposed, he says that the thing proposed is man or animal, he says what it is, and signifies substance; but when white colour being proposed, he says that the thing proposed is white or colour, he says what it is, and signifies quality. So also, if when the magnitude of one cubit is proposed, he says that what is proposed is a cubit in size, he will say what it is, and will signify quantity, and so of the rest, for each of these, both if it be itself predicated of itself, and if genus (be predicated) of it, signifies what a thing is. When however (it is spoken) of another thing, it does not signify what it is, but quantity or quality, or some other category, so that the things about which and from which arguments (subsist), are these and so many; but how we shall take them, and by what we shall be well provided with them, we must declare hereafter.
In the first place then, let us define what is a dialectic proposition, and what a dialectic problem, for we must not suppose every proposition nor every problem as dialectic, since no one in his senses would propose that which is assented to by no one, nor would he advance as a question what was palpable to all, or to most men, for the latter does not admit of a doubt, but the former no one would admit. Indeed a dialectic proposition is an interrogation, probable either to all, or to the most, or to the wise; and to these, either to all or most, or to the most celebrated, it is not paradoxical, as any one may admit what is assented to by the wise, if it be not contrary to the opinions of the multitude. Dialectic propositions however are both those which resemble the probable and which are contrary to those which appear probable, being proposed through contradiction, and whatever opinions are according to the discovered arts. For if it be probable that there is the same science of contraries, it would also appear probable that the sense of contraries is the same, and if the grammatical art be one in number, that there is one art also of playing on the pipe, but if there are many grammatical arts, there will also be many piping arts, for all these things seem to be similar and akin. So also those things which are contrary to probabilities, being proposed according to contradiction, will appear probable, for if it is probable that we ought to benefit friends, it is also probable that we ought not to injure them. Nevertheless, that we ought to injure friends is contrary, but that we ought not to injure them is contradictory; so also if we ought to benefit friends, we ought not to benefit enemies; but this also is according to the contradiction of contraries, since the contrary is that we ought to benefit enemies, and in like manner in the case of other things. Still the probable will appear in comparison to be the contrary about the contrary, as, if we ought to benefit friends, we ought also to injure enemies. To benefit friends however may appear contrary to injuring enemies, yet whether it is truly so or not, will be shown in what we say about contraries. Notwithstanding, it is apparent that whatever opinions also are according to the arts, are dialectic propositions; since any one would admit those things, which are assented to by persons conversant with such subjects, as in matters of medicine, that the physician (is to be assented to), the geometrician in geometrical concerns, and similarly of others.
The dialectic problem is a theorem tending either to choice and avoidance, or to truth and knowledge, either per se or as co-operative with something else of this kind, about which the multitude either hold an opinion in neither way, or in a way contrary to the wise, or the wise to the multitude, or each of these to themselves. Now some problems it is useful to know, for the purpose of choice or avoidance, as whether pleasure is eligible or not, but others for knowledge only, as whether the world is everlasting or not, some again by themselves, for neither of these purposes, yet do they co-operate to something or this kind, since there are many things which we do not desire to know for themselves, but for the sake of others, in order that through these we may know something else. Moreover, those are problems also, of which there are contrary syllogisms (for they admit a doubt, whether they are so and so, because of there being credible arguments in both respects). And those about which we have no argument from their being vast, conceiving it difficult to assign their cause, e. g. whether the world is everlasting or not, for any one may investigate such things as these.
Let then problems and propositions be distinguished as we have said: a thesis, on the other hand, is a paradoxical judgment of some one celebrated in philosophy, as that contradiction is impossible, as Antisthenes said, or that all things are moved, according to Heraclitus, or that being is one, as Melissus asserted, for to notice any casual person setting forth contrarieties to (common) opinions is silly. Or (a thesis is an opinion) of things concerning which we have a reason contrary to opinions, as that not every thing which is, is either generated or perpetual, as the sophists declare, since (they say) that a musician is a grammarian, though he is neither generated nor eternal, for this, even if it be not admitted by any one, may appear to be from possessing a reason.
A thesis then is also a problem, yet not every problem is a thesis, since some problems are of such a kind, as that we form an opinion about them in neither way; but that a thesis is also a problem is evident, as it is neoesary from what we have said, either that the multitude ahould be at variance with the wise about the thesis, or one or other of these with themselves, since a thesis is a certain paradoxical judgment. Now almost all dialectical problems arc called theses, let it, however, make no difference how they are called, as we have not thus divided them from a desire to fabricate names, but that we may not be ignorant what are their real differences.
Still we need not consider every problem nor every thesis, but that which any one may be in doubt about, who is in want of argument and not of punishment or sense, for those who doubt whether we ought to worship the gods and to love our parents or not, require punishment, but those (who doubt) whether snow is white or not, (need) sense. Nor (need we discuss those things) of which the demonstration is at hand, nor those of which it is very remote, for the one do not admit of doubt, but the other, of greater (doubt) than accords to (dialectic) exercise.
These things then being determined, we must distinguish how many species of dialectic arguments there are. Now one is induction, but the other syllogism, and what indeed syllogism is, has been declared before, but induction is a progression from singulars to umversals, as if the pilot skilled in his art is the best, so also is the charioteer, and generally the skilful is the most excellent about each thing. Nevertheless, induction is more calculated to persuade, is clearer, and according to sense more known, and common to many things; but syllogism is more cogent, and efficacious against opponents in disputation.
Let then the genera about which, and from which, arguments subsist be defined, as we have stated before, but the instruments by which we shall be well provided with syllogisms are four; one to assume propositions, the second to be able to distinguish in how many ways each thing is predicated, the third to discover differences, and the fourth the consideration of the similar. In a certain way indeed there are three propositions of these, since it is possible to make a proposition as to each of them, as that the beautiful, or the sweet, or the profitable is eligible, and that sense differs from science, in that he who loses the latter may regain it; but this is impossible with the other, and that the wholesome has the same relation to health as what produces good constitutional habit, to a good habit of constitution. Now the first proposition is derived from that which is predicated in many ways, but the second from differences, and the third from similars.
Propositions then must be selected in as many ways as there has been definition about proposition, either choosing the opinions of all, or those of most, or those of the wise, and of these either of all, or of most, or of the most celebrated, or opinions contrary to the apparent, and whatever are according to arts. Yet it is necessary to propose according to contradiction those which are contrary to the apparently probable, as we observed before; but it is useful to produce them by selecting, not only those which are probable, but those also which are like these, as that there is the same sense of contraries, (for there is the same science,) and that we see by admitting, not by emitting, somewhat, as it is thus also with the other senses, since we both hear from admission and not from emission of something, and also taste, and similarly with the rest. Again, whatever are seen in all or in most things, we must lake as principle and apparent theses, since persons lay down these who do not see, at the same time, in what thing it does not happen so. We must also select from written arguments, but descriptions must he made supposing separately about each genus; as ahout good or about animal, and about every good, beginning from what it is; we must also note besides, the several opinions, as that Empedodes said there are four elements of bodies, for any one would admit what had been asserted by some celebrated man.
But to speak comprehensively, there are three parts of propositions and of problems; for some propositions are ethical, others physical, but others logical. The ethical then are such, as whether it is right to obey parents rather than the laws, if the two are discordant; the logical, as whether there is the same science of contraries or not; and the physical, whether the world is perpetual or not; the like also occurs in problems. Still it is not easy to explain by definition, what the quality of each of the above-named is, but we must endeavour to know each of them from habit, which arises from induction, addressing our attention, according to the before-mentioned examples.
With regard then to philosophy, we must discuss these according to truth; but as to opinion, dialectically; still we must assume all the propositions as universal as possible, and make many one, as that there is the same science of opposites, afterwards that there is of contraries, and also of relatives. In the same manner we must divide these again, as long as it is possible to divide them, as that (there is the same science) of good and of evil, and of white and black, of the cold and the hot, and likewise of other things.
Concerning proposition then, what has been stated will suffice, but as to how many ways (a thing may be predicated), we must discuss not only such things as are predicated in a different manner, but also we must endeavour to give their reasons; as not only that justice and fortitude are called good in one way, but what conduces to a good habit of body and to health in another way, but also that some things (are called so) from being certain qualities, but others from being effective of something, and not from themselves being certain qualities, and indeed in a similar manner in other things.