Again, the generic term and the specific term ought to be univocal in signification. You must examine (according to the tests indicated in the First Book of the Topica) whether it be taken equivocally in the thesis. If it be so, you have a ground of attack, and also if it be taken metaphorically; for every genus ought to be enunciated in the proper sense of the term, and no metaphor can be allowed to pass as a genus.166 Note farther that every true genus has more than one distinct species. You will, therefore, examine whether any other species, besides the subject of the thesis, can be suggested as belonging to the predicate of the thesis. If none, that predicate cannot be the true genus of the subject.167

Several loci are furnished by Contraries, either to the species or the genus. If there be something contrary to the species, but nothing contrary to the genus, then that which is contrary to the species ought to be included under the same genus as the species itself; but, if there be something contrary to the species, and also something contrary to the genus, then that which is contrary to the species ought to be included in that which is contrary to the genus. Each of these doctrines you will have to make good by induction of particular cases.168 If that which is contrary to the species be a genus itself (e.g., bonum) and not included in any superior genus, then the like will be true respecting the species itself: it will not be included in any genus; and the predicate of the thesis will not be a true genus. Bonum and malum are not included in any common superior genus; each is a genus per se.169 Or suppose that the subject (species) of the thesis, and the predicate (genus) of the thesis, have both of them contraries; but that in the one there is an intermediate between the two contraries, and in the other, not. This shows that the predicate cannot be the true genus of the species; for, wherever there is an intermediate between the two contraries of the species, there also is an intermediate between the two contraries of the genus; and vice versÂ.170 If there be an intermediate between the two contraries of the species, and also an intermediate between the two contraries of the genus, you will examine whether both intermediates are of like nature, designated by analogous terms. If it be not so (if, e.g., the one intermediate is designated by a positive term, and the other only by a negative term), you will have ground for contending against the thesis, that the predicate enunciated therein is not the true genus of the subject. At any rate, this is a probable (??d????) dialectical argument — to insist upon analogy between the two intermediates; though there are some particular cases in which the doctrine does not hold.171

Again, suppose different conditions: that there is no contrary to the genus, but that there is a contrary to the species. You will examine whether not merely the contrary of the species, but also the intermediate between its two contraries, is included in the same genus; for, if the two contraries are included therein, the intermediate ought also to be included. This is a line of argument probable (i.e., conformable to general presumption, and recommendable in a dialectical debate), though there are not wanting examples adverse to it: thus, excess and defect are included in the same genus evil, but the moderate or measured (t? ?t????) is not in the genus evil, but in the genus good.172 We must remark, moreover, that though it be a probable dialectical argument, that, wherever the genus has a contrary, the species will also have a contrary, yet there are cases adverse to this principle. Thus, sickness in general has for its contrary health in general; but particular species of sickness (such as fever, ophthalmia, gout, &c.) have no contrary.173

Such will be your way of procedure, if the thesis propounded be Affirmative, and if you have to make out a negative against it. But if, on the contrary, the thesis be Negative, so that you have to make out an affirmative against it, you have then three lines of procedure open. 1. The genus may have no contrary, while the species has a contrary: in that case, you may perhaps be able to show that the contrary of the species (subject) is included in the predicate of the thesis (genus); if so, then the species also will be included therein. 2. Or, if you can show that the intermediate between the species and its contrary is included in the predicate (genus), then that same genus will also include the species and its contrary; for, wherever the intermediate is, there also are the two extremes between which it is intermediate. 3. Lastly, if the genus has a contrary as well as the species, you may be able to show that the contrary of the species is included in the contrary of the genus; assuming which to be the case, then the species itself will be included in the genus.174 These are the three modes of procedure, if your task is to make out the negative.

If the genus enunciated by the thesis be a true one, all the Derivatives and Collaterals of the predicate will be fit and suitable for those of the subject. Thus, if justice be a sort of science, justly will be scientifically, and the just man will be a scientific man. This locus is useful to be kept in mind, whether you have to make out an affirmative or a negative.175 You may reason in the same way about the Analoga of the predicate and the subject; about the productive and destructive causes of each; the manifestations present, past, and future, of each, &c.176

When the opposite of the species (subject) is Privative, the thesis will be open to attack in two ways. 1. If the privative opposite be contained in the predicate, the subject itself will not be contained therein; for it is a general truth that a subject and its privative opposite are never both of them contained in the same lowest genus: thus, if vision is sensible perception, blindness is not sensible perception. 2. If both the species and the genus have privative opposites, then if the privative opposite of the species be contained in the privative opposite of the genus, the species itself will also be contained in the genus; if not, not. Thus, if blindness be an inability of sensible perception, vision will be a sensible perception. This last locus will be available, whether you are making out an affirmative or a negative.177

If the predicate of the thesis be a true genus, you may convert the thesis simply, having substituted for the predicate the denial of its Contradictory; if not, not. Vice versÂ, if the new proposition so formed be true, the predicate of the thesis will be a true genus; if not, not. Thus, if good be the true genus of pleasurable, nothing that is not good will be pleasurable. This locus also will serve both for making out an affirmative and for making out a negative.178

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, ???t?). 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 qu 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