Aristotle

If the subject (species) of the thesis be a Relative, you will examine whether the predicate (genus) be relative also; if not, it will not be the true genus of the subject. The converse of this rule, however, will not hold; and indeed the rule itself is not absolutely universal.179 You may also argue that, if the correlate of the genus be not the same as the correlate of the species, the genus cannot be truly predicated of that species: thus, half is the correlate of double, but half is not the proper correlate of multiple; therefore, multiple is not the true genus of double. But your argument may here be met by contradictory instances; thus, cognition has reference to the cognitum, but habitus and dispositio (the genera to which cognitio belongs) do not refer to cognitum but to anima.180 You may also examine whether the correlate, when applied to the genus, is put in the same case (e.g., genitive, dative, &c.) as when it is applied to the species: if it be put into a different case, this affords presumption that the genus is not a true genus; though here again instances may be produced showing that your presumption will not hold universally. Farther, you will observe whether the correlates thus similarly inflected reciprocate like the species and genus; if not, this will furnish you with the same adverse presumption.181

Again, examine whether the correlate of the genus is genus to the correlate of the species; if it be not so, you may argue that the genus is not truly predicated. Thus, if the thesis affirms that perceptio is the genus of cognitio, it will follow that percipibile is the genus of cognoscibile. Now this cannot be maintained; for there are some cognoscibilia which are not perceivable, e.g., some cogitabilia (intelligibilia, νοητά). Since therefore percipibile is not the true genus of cognoscibile, neither can perceptio be the true genus of cognitio.182

Suppose the thesis predicates of memory that it is — a continuance of cognition. This will be open to attack, if the predicate be affirmed as the genus (or even as the accident) of the subject. For every continuance must be in that which continues. But memory is of necessity in the soul; it cannot therefore be in cognition.183 There is another ground on which the thesis will be assailable, if it defines memory to be — a habit or acquirement retentive of belief. This will not hold, because it confounds habit or disposition with act; which last is the true description of memory. The opposite error will be committed if the respondent defines perceptivity to be a — movement through or by means of the body. Here perceptivity, which is a habit or disposition, is ranked under movement, which is the act exercising the same, i.e., perceptivity in actual exercise.184 Or, the mistake may be made of ranking some habit or disposition under the power consequent on the possession thereof, as if this power were the superior genus: thus the respondent may define gentleness to be a continence of anger; courage, a continence of fears; justice, a continence of appetite of lucre. But the genus here assigned is not a good one: for a man who feels no anger is called gentle; a man who feels no fear is called courageous; whereas the continent man is he who feels anger or fear, but controls them. Such controlling power is a natural consequence of gentleness and courage, insomuch that, if the gentle man happened to feel anger, or the courageous man to feel fear, each would control these impulses; but it is no part of the essence thereof, and therefore cannot be the genus under which they fall.185 A like mistake is made if pain be predicated as the genus of anger, or supposition as the genus of belief. The angry man doubtless feels pain, but his pain precedes his anger in time, and is the antecedent cause thereof; now the genus can never precede its species in time. So also a man may have the same supposition sometimes with belief, sometimes without it; accordingly, supposition cannot be the genus of belief any more than the same animal can be sometimes a man, sometimes a brute.186 And indeed the same negative conclusion would follow, even if we granted that every supposition was always attended with belief. For, in that case, supposition and belief would be co-extensive terms; but the generic term must always be more extensive than its specific.187

You will farther examine whether the predicate of the thesis be of a nature to inhere in the same substance as the subject. If it be not, it cannot be truly predicated thereof, either as genus or even as accident. White (species) and colour (genus) are of a nature to inhere or belong to the same substance. But, if the thesis declares that shame is a species of fear, or that anger is a species of pain, you may impugn it on the ground that shame belongs to the reasoning element in man, fear to the courageous or energetic element; and that pain belongs to the appetitive element, anger to the courageous. This proves that fear can neither be the genus nor the accident of shame; that pain can neither be the genus nor the accident of anger.188

Suppose the thesis declares that animal is a species under the genus visibile or percepibile. You may oppose it by pointing out that animal is only visibile secundum quid, or partially; that is, only so far as regards body, not as regards mind. But the species always partakes of its genus wholly, not partially or secundum quid; thus, man is not partially animal, but wholly or essentially animal. If what is predicated as the genus be not thus essentially partaken, it cannot be a true genus; hence neither visibile nor percepibile is a true genus of animal.189

Sometimes what is predicated as the genus is, when compared to its species, only as a part to the whole; which is never the case with a true genus. Some refer animal to the genus living body; but body is only part of the whole animal, and therefore cannot be the true genus thereof.190 Sometimes a species which is blameworthy and hateful, or a species which is praiseworthy and eligible, may be referred to the power or capacity from which it springs, as genus; thus, the thief, a blameworthy and hateful character, may be referred to the predicate — capable of stealing another man’s property. But this, though true as a predicate, is not the true genus; for the honest man is also capable of so acting, but he is distinguished from the thief by not acting so, nor having the disposition so to act. All power and capacity is eligible; if the above were the true genus of thief, it would be a case in which power and capacity is blameworthy and hateful. Neither, on the other hand, can any thing in its own nature praiseworthy and eligible, be referred to power and capacity as its genus; for all power and capacity is praiseworthy and eligible not in itself or its own nature, but by reason of something else, namely, its realizable consequences.191

Again, you may detect in the thesis sometimes the mistake of putting under one genus a species which properly comes under two genera conjointly, not subalternate one to the other; sometimes, the mistake of predicating the genus as a differentia, or the differentia as a genus.192 Sometimes, also, the subject in which the attribute or affection resides is predicated as if it were the genus of such affection; or, è converso, the attribute or affection is predicated as the genus of the subject wherein it resides; e.g., when breath or wind, which is really a movement of air, is affirmed to be air put in motion, and thus constituted as a species under the genus air; or when snow is declared to be water congelated; or mud, to be earth mixed with moisture.193 In none of these cases is the predicate a true genus; for it cannot be always affirmed of the subject.

Or perhaps the predicate affirmed as genus may be no genus at all; for nothing can be a genus unless there are species contained under it; e.g., if the thesis declare white to be a genus, this may be impugned, because white objects do not differ in specie from each other. Or a mere universal predicate (such as Ens or Unum) may be put forward as a genus or differentia; or a simple concomitant attribute, or an equivocal term, may be so put forward.194

Perhaps it may happen that the subject (species) and the predicate (genus) of the thesis may each have a contrary term; and that in each pair of contrary terms one may be better, the other worse. If, in that case, the better species be referred to the worse genus, or vice versâ, this will render the thesis assailable. Or perhaps the species may be fit to be referred equally to both the contrary genera; in which case, if the thesis should refer it to the worse of the two, that will be a ground of objection. Thus, if the soul be referred to the genus mobile, you are at liberty to object that it is equally referable to the genus stabile: and that, as the latter is the better of the two, it ought to be referred to the better in preference to the worse.195

There is a locus of More and Less, which may be made available in various ways. Thus, if the genus predicated admits of being graduated as more or less, while the species of which it is predicated does not admit of such graduation, you may question the applicability of the genus to the species.196 You may raise the question also, if there be any thing else which looks equally like the true genus, or more like it than the genus predicated by the thesis. This will happen often, when the essence of the species includes several distinct elements; e.g., in the essence of anger, there is included both pain (an emotional element), and the supposition or belief of being undervalued (an intellectual element); hence, if the thesis ranks anger under the genus pain, you may object that it equally belongs to the genus supposition197 This locus is useful for raising a negative question, but will serve little for establishing an affirmative. Towards the affirmative, you will find advantage in examining the subject (species) respecting which the thesis predicates a given genus; for, if it can be shown that this supposed species is no real species but a genus, the genus predicated thereof will be à fortiori a genus.198

Some think (says Aristotle)199 that Differentia as well as Genus is predicated essentially respecting the Species. Accordingly, Genus must be discriminated from Differentia. For such discrimination the following characteristics are pointed out:— 1. Genus has greater extent in predication than Differentia. 2. In replying to the enquiry, Quid est? it is more suitable and significant to declare the Genus than the Differentia. 3. Differentia declares a quality of Genus, and therefore presupposes Genus as already known; but Genus does not in like manner presuppose Differentia. If you wish to show that belief is the genus to which cognition belongs, you must examine whether the cognoscens believes quâ cognoscens. If he does so, your point is made out.200

Wherever a predicate is universally true of its subject, while the proposition is not true if simply converted (i.e., wherever the predicate is of larger extension than the subject), there is difficulty in distinguishing it from a genus. Accordingly, when you are respondent, maintaining the affirmative side, you will use such predicate as if it were a genus; but, when you are assailant, you will not allow the respondent to do so. You may quote against him the instance of Non-Ens; which is predicable of every thing generated, but which is not a genus, since it has no species under it.201

V.

Aristotle passes, in the Fifth book of the Topica, to those debates in which the thesis set up declares the predicate as Proprium of the subject.

A Proprium may belong to its subject either per se and semper, or relatively to something else and occasionally or sometimes. It is a proprium per se of man to be an animal by nature tractable. It is a relative proprium of the soul in regard to the body, to exercise command; of the body in regard to the soul, to obey command. It is a proprium semper of a god, to be immortal; it is an occasional proprium (i.e., sometimes) of this or that man, to be walking in the market-place.202 When the proprium is set out relatively to something else, the debate must involve two questions, and may involve four. Thus, if the thesis affirms that it is a proprium of man relatively to horse (discriminating man from horse) to be by nature two-footed, you may (as opponent) either deny that man is two-footed, or affirm that horse is two-footed; or you may go farther and affirm that man is by nature four-footed, or deny that horse is by nature four-footed. If you can succeed in showing any one of these four, you will have refuted the thesis.203

The Proprium per se discriminates its subject from everything else, and is universally true thereof; the relative Proprium discriminates its subject only from some other assignable subject. The relative Proprium may be either constant and universally true, or true with exceptions — true and applicable in the ordinary course of things: it may be tested through those Loci which have been enumerated as applicable to the Accident. The Proprium per se, and the constant Proprium, have certain Loci of their own, which we shall now indicate. These are the most logical (sensu Aristotelico) or suitable for Dialectic; furnishing the most ample matter for debates.204

Aristotle distinguishes (1) those cases in which the alleged proprium is a true proprium, but is incorrectly or informally set out in the thesis, from those (2) in which it is untruly predicated, or is no proprium at all.

To set out a proprium well, that which is predicated ought to be clearer and better known than the subject of which it is predicated, since the purpose of predicating the proprium is to communicate knowledge.205 If it be more obscure or less known, you may impugn the thesis as bad in form, or badly set out. Thus, if the thesis declare, as a proprium of fire, that fire is of all things the most like to the soul, this is not well set out, because the essence of the soul is not so well known as the essence of fire. Moreover, the fact that the predicate belongs to the subject, ought to be better known even than the subject itself; for whoever is ignorant that A belongs to B at all, cannot possibly know that A is the proprium of B.206 Thus, if the thesis declare, as proprium of fire, that it is the first or most universal subject in which it is the nature of soul to be found, the predicate is here doubly unknowable: first, the hearer does not know that the soul is found in fire at all; next, he does not know that fire is the first subject in which soul is found. On the other hand, the respondent will repel your attack if he can show that his proprium is more knowable in both the two above-mentioned ways. If, for example, he declares as thesis, To have sensible perception is the proprium of an animal, here the proprium is both well known in itself, and well known as belonging to the given subject. Accordingly, it is well set out, as far as this condition is concerned.207

A second condition of its being well set out is, that it shall contain neither equivocal term nor equivocal or amphibolical proposition. Thus, if the thesis declares, To perceive is the proprium of an animal, it is equivocal; for it may mean either to have sensible perception, or to exercise sensible perception actually. You may apply the test to such a thesis, by syllogizing from one or both of these equivocal meanings. The respondent will make good his defence, if he shows that there is no such equivocation: as, for example, if the thesis be, It is a proprium of fire to be the body most easily moved into the upper region; where there is no equivocation, either of term or proposition.208 Sometimes the equivocation may be, not in the name of the proprium itself, but in the name of the subject to which it is applied. Where this last is not unum et simplex but equivocal, the thesis must specify which among the several senses is intended; and, if that be neglected, the manner of setting out is incorrect.209

Another form of the like mistake is, where the same term is repeated both in the predicate and in the subject; which is often done, both as to Proprium and as to Definition, though it is a cause of obscurity, as well as a tiresome repetition.210 The repetition may be made in two ways: either directly, by the same term occurring twice; or indirectly, when the second term given is such that it cannot be defined without repeating the first. An example of direct repetition is, Fire is a body the rarest among bodies (for proprium of fire). An example of indirect repetition is, Earth is a substance which tends most of all bodies downwards to the lowest region (as proprium of earth); for, when the respondent is required to define bodies, he must define them — such and such substances.211 An example free from objection on this ground is, Man is an animal capable of receiving cognition (as proprium of man).

Another mode of bad or incorrect setting out is, when the term predicated as proprium belongs not only to the subject, but also to all other subjects. Such a proposition is useless; for it furnishes no means of discriminating the subject from anything; whereas discrimination is one express purpose of the Proprium as well as of the Definition.212 Again, another mode is, when the thesis declares several propria belonging to the same subject, without announcing that they are several. As the definer ought not to introduce into his definition any words beyond what are required for declaring the essence of the subject, so neither should the person who sets out a proprium add any words beyond those requisite for constituting the proprium. Thus, if the thesis enunciates, as proprium of fire, that it is the thinnest and lightest body, here are two propria instead of one. Contrast with this another proprium, free from the objection just pointed out — Moist is that which may assume every variety of figure.213

A farther mistake is, when the predicate declaring the proprium includes either the subject itself or some species comprehended under the subject; for example, when we are told, as a proprium of animal, that animal is a substance of which man is a species. We have already seen that the proprium ought to be better known than its subject; but man is even less known (posterior in respect to cognition) than animal, because it is a species under the genus animal.214

Again, our canon — That the Proprium should be better known than its subject, or should make the subject better known — will be violated in another way, if the proprium enunciated be something opposite to the subject, or in any other way simul naturâ as compared with the subject; and still more, if it be posterius naturâ as compared with the subject. Thus, if a man enunciates, as proprium of good, that good is that which is most opposite to evil, his proprium will not be well or correctly set out.215

Perhaps, again, the thesis may enunciate as proprium what is not constantly appurtenant to the subject, but is sometimes absent therefrom; or, intending to enunciate an occasional proprium, it may omit to specify the qualifying epithet occasional. In either case the proprium is not well set out, and a ground is furnished for censure, which ought always to be avoided.216