Nothing else except Genera and Species can be called Second Essences, or said to belong to the Category Essence; for they alone declare what the First Essence is. If you are asked respecting Sokrates, What he is? and if you answer by stating the Species or the Genus to which he belongs — that he is a man or an animal — your answer will be appropriate to the question; and it will be more fully understood if you state the Species than if you state the Genus. But if you answer by stating what belongs to any of the other Categories (viz., that he is white, that he is running), your answer will be inappropriate, and foreign to the question; it will not declare what Sokrates is.37 Accordingly, none of these other Categories can be called Essences. All of them rank as predicates both of First and of Second Essence; just as Second Essences rank as predicates of First Essences.38

Essence or Substance is not in a Subject; neither First nor Second Essence. The First Essence is neither in a Subject nor predicated of a Subject; the Second Essences are not in the First, but are predicated of the First. Both the Second Essence, and the definition of the word describing it, may be predicated of the First; that is, the predication is synonymous or univocal; whereas, of that which is in a Subject, the name may often be predicated, but never the definition of the name. What is true of the Second Essence, is true also of the Differentia; that it is not in a Subject, but that it may be predicated univocally of a Subject — not only its name, but also the definition of its name.39

All Essence or Substance seems to signify Hoc Aliquid Unum Numero. The First Essence really does so signify, but the Second Essence does not really so signify: it only seems to do so, because it is enunciated by a substantive name, like the First.40 It signifies really Tale Aliquid, answering to the enquiry Quale Quid? for it is said not merely of one thing numerically, but of many things each numerically one. Nevertheless, a distinction must be drawn. The Second Essence does not (like the Accident, such as white) signify Tale Aliquid simply and absolutely, or that and nothing more. It signifies Talem Aliquam Essentiam; it declares what the Essence is, or marks off the characteristic feature of various First Essences, each Unum Numero. The Genus marks off a greater number of such than the Species.41

Again, Essences have no contraries.42 But this is not peculiar to Essences, for Quanta also have no contraries; there is nothing contrary to ten, or to that which is two cubits long. Nor is any one of the varieties of First Essence more or less Essence than any other variety. An individual man is as much Essence as an individual horse, neither more nor less. Nor is he at one time more a man than he was at another time; though he may become more or less white, more or less handsome.43

But that which is most peculiar to Essence, is, that while remaining Unum et Idem Numero, it is capable by change in itself of receiving alternately contrary Accidents. This is true of no other Category. For example, this particular colour, being one and the same in number, will never be now black, and then white; this particular action, being one and the same in number, will not be at one time virtuous, at another time vicious. The like is true respecting all the other Categories. But one and the same man will be now white, hot, virtuous; at another time, he will be black, cold, vicious. An objector may say that this is true, not merely of Essence, but also of Discourse and of Opinion; each of which (he will urge) remains Unum Numero, but is nevertheless recipient of contrary attributes; for the proposition or assertion, Sokrates is sitting, may now be true and may presently become false. But this case is different, because there is no change in the proposition itself, but in the person or thing to which the proposition refers; while one and the same man, by new affections in himself, is now healthy, then sick; now hot, then cold.44

Here Aristotle concludes his first Category or Predicament — Essence or Substance. He proceeds to the other nine, and ranks Quantity first among them.45 Quantum is either Continual or Discrete; it consists either of parts having position in reference to each other, or of parts not having position in reference to each other. Discrete Quanta are Number and Speech; Continual Quanta are Line, Surface, Body, and besides these, Time and Place. The parts of Number have no position in reference to each other; the parts of Line, Surface, Body, have position in reference to each other. These are called Quanta, primarily; other things are called Quanta in a secondary way, κατὰ συμβεβηκός.46 Thus we say much white, when the surface of white is large; we say, the action is long, because much time and movement have been consumed in it. If we are asked, how long the action is? we must answer by specifying its length in time — a year or a month.

To Quantum (as to Essence or Substance) there exists no contrary.47 There is nothing contrary to a length of three cubits or an area of four square feet. Great, little, long, short, are more properly terms of Relation than terms of Quantity; thus belonging to another Category. Nor is Quantum ever more or less Quantum; it does not admit of degree. The Quantum a yard is neither more nor less Quantum than that called a foot. That which is peculiar to Quanta is to be equal or unequal:48 the relations of equality and inequality are not properly affirmed of anything else except of Quanta.

From the Category of Quantity, Aristotle proceeds next to that of Relation;49 which he discusses in immediate sequence after Quantity, and before Quality, probably because in the course of his exposition about Quantity, he had been obliged to intimate how closely Quantity was implicated with Relation, and how essential it was that the distinction between the two should be made clear.

Relata (τὰ πρός τι — ad Aliquid) are things such, that what they are, they are said to be of other things, or are said to in some other manner towards something else (ὅσα αὐτὰ ἅπερ ἐστὶν ἑτέρων εἶναι λέγεται, ἢ ὁπωστοῦν ἄλλως πρὸς ἕτερον). Thus, that which is greater, is said to be greater than another; that which is called double is called also double of another. Habit, disposition, perception, cognition, position, &c., are all Relata. Habit, is habit of something; perception and cognition, are always of something; position, is position of something. The Category of Relation admits contrariety in some cases, but not always; it also admits, in some cases, graduation, or the more or less in degree; things are more like or less like to each other.50 All Relata are so designated in virtue of their relation to other Correlata; the master is master of a servant — the servant is servant of a master. Sometimes the Correlatum is mentioned not in the genitive case but in some other case; thus cognition is cognition of the cognitum, but cognitum is cognitum by cognition; perception is perception of the perceptum, but the perceptum is perceptum by perception.51 The correlation indeed will not manifestly appear, unless the Correlate be designated by its appropriate term: thus, if the wing be declared to be wing of a bird, there is no apparent correlation; we ought to say, the wing is wing of the winged, and the winged is winged through or by the wing; for the wing belongs to the bird, not quâ bird, but quâ winged,52 since there are many things winged, which are not birds. Sometimes there is no current term appropriate to the Correlate, so that we are under the necessity of coining one for the occasion: we must say, to speak with strict accuracy, ἡ κεφαλή, τοῦ κεφαλωτοῦ κεφαλή not ἡ κεφαλή, τοῦ ζῷου κεφαλή; τὸ πηδάλιον, τοῦ πηδαλιωτοῦ πηδάλιον, not τὸ πηδάλιον, πλοίου πηδάλιον.53

The Relatum and its Correlate seem to be simul naturâ. If you suppress either one of the pair, the other vanishes along with it. Aristotle appears to think, however, that there are many cases in which this is not true. He says that there can be no cognoscens without a cognoscibile, nor any percipiens without a percipibile; but that there may be cognoscibile without any cognoscens, and percipibile without any percipiens. He says that τὸ αἰσθητὸν exists πρὸ τοῦ αἴσθησιν εἶναι.54 Whether any Essence or Substance can be a Relatum or not, he is puzzled to say; he seems to think that the Second Essence may be, but that the First Essence cannot be so. He concludes, however, by admitting that the question is one of doubt and difficulty.55

Quality is that according to which Subjects are called Such and Such (ποιοί τινες). It is, however, not a true genus, but a vague word, of many distinct, though analogous, meanings including an assemblage of particulars not bound together by any generic tie.56 The more familiar varieties are — 1. Habits or endowments (ἕξεις) of a durable character, such as, wise, just, virtuous; 2. Conditions more or less transitory, such as, hot, cold, sick, healthy, &c. (διαθέσεις); 3. Natural powers or incapacities, such as hard, soft, fit for boxing, fit for running, &c. 4. Capacities of causing sensation, such as sweet of honey, hot and cold of fire and ice. But a person who occasionally blushes with shame, or occasionally becomes pale with fear, does not receive the designation of such or such from this fact; the occasional emotion is a passion, not a quality.57

A fifth variety of Quality is figure or circumscribing form, straightness or crookedness. But dense, rare, rough, smooth, are not properly varieties of Quality; objects are not denominated such and such from these circumstances. They rather declare position of the particles of an object in reference to each other, near or distant, evenly or unevenly arranged.58

Quality admits, in some cases but not in all, both contrariety and graduation. Just is contrary to unjust, black to white; but there is no contrary to red or pale. If one of two contraries belongs to Quality, the other of the two will also belong to Quality. In regard to graduation, we can hardly say that Quality in the abstract is capable of more and less; but it is indisputable that different objects have more or less of the same quality. One man is more just, healthy, wise, than another; though justice or health in itself cannot be called more or less. One thing cannot be more a triangle, square, or circle than another; the square is not more a circle than the oblong.59

What has just been said is not peculiar to Quality; but one peculiarity there is requiring to be mentioned. Quality is the foundation of Similarity and Dissimilarity. Objects are called like or unlike in reference to qualities.60

In speaking about Quality, Aristotle has cited many illustrations from Relata. Habits and dispositions, described by their generic names, are Relata; in their specific varieties they are Qualities. Thus cognition is always cognition of something, and is therefore a Relatum; but grammatiké (grammatical cognition) is not grammatiké of any thing, and is therefore a Quality. It has been already intimated61 that the same variety may well belong to two distinct Categories.

After having thus dwelt at some length on each of the first four Categories, Aristotle passes lightly over the remaining six. Respecting Agere and Pati, he observes that they admit (like Quality) both of graduation and contrariety. Respecting Jacēre he tells us that the predicates included in it are derived from the fact of positions, which positions he had before ranked among the Relata. Respecting Ubi, Quando, and Habere, he considers them all so manifest and intelligible, that he will say nothing about them; he repeats the illustrations before given — Habere, as, to be shod, or to be armed (to have shoes or arms); Ubi, as, in the Lykeium; Quando, as, yesterday, last year.62

No part of the Aristotelian doctrine has become more incorporated with logical tradition, or elicited a greater amount of comment and discussion,63 than these Ten Categories or Predicaments. I have endeavoured to give the exposition as near as may be in the words and with the illustrations of Aristotle; because in many of the comments new points of view are introduced, sometimes more just than those of Aristotle, but not present to his mind. Modern logicians join the Categories side by side with the five Predicables, which are explained in the Eisagoge of Porphyry, more than five centuries after Aristotle’s death. As expositors of Logic they are right in doing this; but my purpose is to illustrate rather the views of Aristotle. The mind of Aristotle was not altogether exempt from that fascination64 which particular numbers exercised upon the Pythagoreans and after them upon Plato. To the number Ten the Pythagoreans ascribed peculiar virtue and perfection. The fundamental Contraries, which they laid down as the Principles of the Universe, were ten in number.65 After them, also, Plato carried his ideal numbers as far as the Dekad, but no farther. That Aristotle considered Ten to be the suitable number for a complete list of general heads — that he was satisfied with making up the list of ten, and looked for nothing beyond — may be inferred from the different manner in which he deals with the different items. At least, such was his point of view when he composed this treatise. Though he recognizes all the ten Categories as co-ordinate in so far that (except Quale) each is a distinct Genus, not reducible under either of the others, yet he devotes all his attention to the first four, and gives explanations (copious for him) in regard to these. About the fifth and sixth (Agere and Pati)66 he says a little, though much less than we should expect, considering their extent and importance. About the last four, next to nothing appears. There are even passages in his writings where he seems to drop all mention of the two last (Jacere and Habere), and to recognize no more than eight Predicaments. In the treatise Categoriæ where his attention is fastened on Terms and their signification, and on the appropriate way of combining these terms into propositions, he recites the ten seriatim; but in other treatises, where his remarks bear more upon the matter and less upon the terms by which it is signified, he thinks himself warranted in leaving out the two or three whose applications are most confined to special subjects. If he had thought fit to carry the total number of Predicaments to twelve or fifteen instead of ten,67 he would probably have had little difficulty in finding some other general heads not less entitled to admission than Jacere and Habere; the rather, as he himself allows, even in regard to the principal Categories, that particulars comprised under one of them may also be comprised under another, and that there is no necessity for supposing each particular to be restricted to one Category exclusively.

These remarks serve partly to meet the difficulties pointed out by commentators in regard to the Ten Categories. From the century immediately succeeding Aristotle, down to recent times, the question has always been asked, why did Aristotle fix upon Ten Categories rather than any other number? and why upon these Ten rather than others? And ancient commentators68 as well as modern have insisted, that the classification is at once defective and redundant; leaving out altogether some particulars, while it enumerates others twice over or more than twice. (This last charge is, however, admitted by Aristotle himself, who considers it no ground of objection that the same particular may sometimes be ranked under two distinct heads.) The replies made to the questions, and the attempts to shew cause for the selection of these Ten classes, have not been satisfactory; though it is certain that Aristotle himself treats the classification as if it were real and exhaustive,69 obtained by comparing many propositions and drawing from them an induction. He tries to determine, in regard to some particular enquiries, under which of the Ten Summa Genera the subject of the enquiry is to be ranged; he indicates some predicate of extreme generality (Unum, Bonum, &c.), which extend over all or several Categories, as equivocal or analogous, representing no true Genera. But though Aristotle takes this view of the completeness of his own classification, he never assigns the grounds of it, and we are left to make them out in the best way we can.

We cannot safely presume, I think, that he followed out any deductive principle or system; if he had done so, he would probably have indicated it. The decuple indication of general heads arose rather from comparison of propositions and induction therefrom. Under each of these ten heads, some predicate or other may always be applied to every concrete individual object, such as a man or animal. Aristotle proceeded by comparing a variety of propositions, such as were employed in common discourse or dialectic, and throwing the different predicates into genera, according as they stood in different logical relation to the Subject. The analysis applied is not metaphysical but logical; it does not resolve the real individual into metaphysical ἀρχαὶ or Principles, such as Form and Matter; it accepts the individual as he stands, with his full complex array of predicates embodied in a proposition, and analyses that proposition into its logical constituents.70 The predicates derive their existence from being attached to the First Subject, and have a different manner of existence according as they are differently related to the First Subject.71 What is this individual, Sokrates? He is an animal. What is his Species? Man. What is the Differentia, limiting the Genus and constituting the Species? Rationality, two-footedness. What is his height and bulk? He is six feet high, and is of twelve stone weight. What manner of man is he? He is flat-nosed, virtuous, patient, brave. In what relation does he stand to others? He is a father, a proprietor, a citizen, a general. What is he doing? He is digging his garden, ploughing his field. What is being done to him? He is being rubbed with oil, he is having his hair cut. Where is he? In the city, at home, in bed. When do you speak of him? As he is, at this moment, as he was, yesterday, last year. In what posture is he? He is lying down, sitting, standing up, kneeling, balancing on one leg. What is he wearing? He has a tunic, armour, shoes, gloves.