Our knowledge of Hindu philosophy, and of the relations in which it may have stood to Greek speculation, is not yet adequate to give decisive answers to various questions that naturally arise on observation of their many resemblances , and it might therefore appear irrelevant to introduce into an historical notice of a peculiarly Western doctrine any reference to its Eastern counterpart. Yet the similarity between the two is so striking that, if not historically connected, they must at least be regarded as expressions of similar philosophic wants. The Hindu classification to which we specially refer is that of Kanada, who lays down six categories, or classes of existence, a seventh being generally added by the commentators. The term employed is Padârtha, meaning “signification of a word.” This is in entire harmony with the Aristotelian doctrine, the categories of which may with truth be described as significations of simple terms, τα κατά μηδεμiav συμπλοκήν Χεγόμενα. The six categories of Kanada are Substance, Quality, Action, Genus, Individuality, and Concretion or Co-inherence. To these is added Non-Existence, Privation, or Negation. Substance is the permanent sub-strate in which Qualities exist. Action, belonging to or inhering in substances, is that which produces change. Genus belongs to substance, qualities, and actions; there are higher and lower genera. Individuality, found only in substance, is that by which a thing is self-existent and marked off from others. Concretion or Co-inherence denotes inseparable or necessary connection, such as that between substance and quality. Under these six classes, γένη τoυ ovτoς, Kanada then proceeds to range the facts of the universe.

Within Greek philosophy itself there were foreshadowings of the Aristotelian doctrine, but nothing so important as to warrant the conclusion that Aristotle was directly influenced by it. Doubtless the One and Many, Being and Non-Being, of the Eleatic dialectic, with their subordinate oppositions, may be called categories, but they are not so in the Aristotelian sense, and have little or nothing in common with the later system. Their starting-point and results are wholly diverse. Nor does it appear necessary to do more than mention the Pythagorean table of principles, the number of which is supposed to have given rise to the decuple arrangement adopted by Aristotle. The two classifications have nothing in common; no term in the one list appears in the other; and there is absolutely nothing in the Pythagorean principles which could have, led to the theory of the categories.

One naturally turns to Plato when endeavouring to discover the genesis of any Aristotelian doctrine, and undoubtedly there are in the Platonic writings many detached discussions in which the matter of the categories is touched upon. Special terms also are anticipated at various times, e.g., πιοιότης in the Theoetetus, πoιεlv and πάσχαν in the Gorgias, and πρός τι in the Sophist. But there does not seem to be anything in Plato which one could say gave occasion directly and of itself to the Aristotelian doctrine; and even when we take a more comprehensive view of the Platonic system and inquire what in it corresponds to the widest definition of categories, say as ultimate elements of thought and existence, we receive no very definite answer. The Platonic dialectic never worked, out into system, and only in two dialogues do we get anything like a list of ultimate or root-notions. In the Sophist, Being, Rest, and Motion (το ον αυτό καί στάσιν καί κίνησις) are laid down as μέγιστα τών yevωv. i To these are presently added the Same and the Other (τaiτov κai θάτερον), and out of the consideration of all five some light is cast upon the obscure notion of Non-Being (tò μη 5v). In the same dialogue (262, sç.) is found the important distinction of όνομα and ρήμα, noun and verb. The Philebus presents us with a totally distinct classification into four elements—the Infinite, the Finite, the Mixture or Unity of both, and the Cause of this unity (το άπειρον, το πέρας, ή σύμμιξις, ή αίτια). It is at once apparent that, however these classifications are related to one another and to the Platonic system, they lie in a different field from that occupied by the Aristotelian categories, and can hardly be said to have anything in common with them.

The Aristotelian doctrine is most distinctly formulated in the short treatise Kaτηγopiaι, which generally occupies the first place among the books of the Organon. The authenticity of the treatise was doubted in early times by some of the commentators,· and the doubts have been revived by such scholars as Spengel and Prantl. On the other hand Brandis, Bonitz, and Zeller are of opinion that the tract is substantially Aristotle’s. The matter is hardly one that can be decided either pro or con with anything like certainty; but this is of little moment, for the doctrine of the categories, even of the ten categories, does not stand or fall with only one portion of Aristotle’s works.

It is surprising that there should yet be so much uncertainty as to the real significance of the categories, and that we should be in nearly complete ignorance as to the process of thought by which Aristotle was led to the doctrine. On both points it is difficult to extract from the matter before us anything approaching a satisfactory solution. The terms employed to denote the categories have been scrutinized with the utmost care, but they give little help. The most important— κ∙ τoυ Svτoς or τής ουσίας, γένη τού Õvtoç or τών ovτωv, γένη simply, τα πρώτα or τα κοινά πρώτα, αί τττώσιίί, or αί διαιρέσεις— only indicate that the categories are general classes into which Being as such may be divided, that they are summa genera. The expressions γένη τών κατηγοριών and σχήματα τών κ., which are used frequently, seem to lead to another and somewhat different view. Κατηγορία being taken to mean that which is predicated, γένη τών κ. would signify the most general classes of predicates, the framework into the divisions of which all predicates must come. To this interpretation there are objections. The categories must be carefully distinguished from predicables; in the scholastic phraseology the former refer to first intentions, the latter to second intentions, i.e., the one denote real, the other logical connection. Further, the categories cannot without careful explanation be defined as predicates; they are this and something more. The most important category, ουσία, in one of its aspects cannot be predicate at all.

In the Kα-∏7γ0piαι Aristotle prefixes to his enumeration a grammatico-logical disquisition on homonyms and synonyms, and on the elements of the proposition, i.e., subject and predicate. He draws attention to the fact that things are spoken of either in the connection known as the proposition, e.g., “a man runs,” or apart from such connection, e.g., “man” and “runs.” He then proceeds, “Of things spoken of apart from their connection in a proposition (των κατά μηδeμiαv συμπλοκήν λtγoμivωv), each signifies either Substance (ουσία), or Quantity (πoσo'v),or Quality (ποιόν), or Relation (πρός τι), or Where (ι.e. Place, που), or When (i.e. Time, πoτε), or Position (κεiσ0αt), or Possession (εχειv), or Action (πoιειv), or Passion (πάσχαν). Ουσία, the first category, is subdivided into πρώτη ουσία or primary substance, which is defined to be τόδε τι, the singular thing in which properties inhere, and to which predicates are attached, and δευτεpαι oυσiaι, genera or species which can be predicated of primary substances, and are therefore ουσία only in a secondary sense. Nevertheless, they too, after a certain fashion, signify the singular thing, τo'δε τι (K., p. 3b, 12, 13). It is this doctrine of πρώτη ουσία that has raised doubts with regard to the authenticity of the Kαττp γoplαι. But the tenfold classification, which has also been captiously objected to, is given in an acknowledged writing of Aristotle’s (see Topicà, i. 9, p. 103b, 20). At the same time it is at least remarkable that in two places where the enumeration seems intended to be complete (Met., p. 1017a, 25; An. Bos., i. 22, p. 83a, 21), only eight are mentioned, eχav and κaσθαο being omitted. In other passages six, five, four, and three are given, frequently with some addition, such as καi at aλλaι κ. It is also to be observed that, despite of this wavering, distinct intimations are given by Aristotle that he regarded his list as complete, and he uses phrases which would seem to indicate that the division had been exhaustively carried out. He admits certainly that some predicates which come under one category might be referred to another, but he declines to deduce all from one highest class, or to recognize any relation of subordination among the several classes.

The full import of the categories will never be adequately reached from the point of view taken up in the Kατ7γ0piαι, which bears all the marks of an early and preliminary study. For true understanding we must turn to the Metaphysics, where the doctrine is handled at large. The discussion of Being in that work starts with a distinction that at once gives us a clue. Tò õv is spoken of in many ways; of these four are classified—το δv κατά συμβeβηκoς, το δv ως αληθiς, to δv δυνάμει καi εvepγeiα, and το δv κατά τα σχήματα των κατηγοριών. It is evident from this that the categories can be regarded neither as purely logical nor as purely metaphysical elements. They indicate the general forms or ways in which Being can be predicated; they are determinations of Being regarded as an object of thought, and consequently as matter of speech. It becomes apparent also why the analysis of the categories starts from the singular thing, for it is the primary form under which all that is becomes object of knowledge, and the other categories modify or qualify this real individual. Πάντα δε τα γιγνόμενα υπό τε τίνος γίγνεται καί ίκ τίνος και τί. Tò δε τί λέγω καθ’ ίκάστην κατηγορίαν’ η γαρ τόδε η ποσον η ποών η που (Met., ρ. 1032a, 13—15). . . . The categories, therefore, are not logical forms but real predicates; they are the general modes in which Being may be expressed. The definite thing, that which comes forward in the process from potentiality to full actuality, can only appear and be spoken of under forms of individuality, quality, quantity, and so on. The nine later categories all denote entity in a certain imperfect fashion.

The categories then are not to be regarded as heads of predicates, the framework into which predicates can be thrown. They are real determinations of Being— allgemeine Bestimmtheiten, as Hegel calls them. They are not summa genera of existences, still less are they to be explained as a classification of nameable things in general. The objections Mill has taken to the list are entirely irrelevant, and would only have significance if the categories were really—what they are not—an exhaustive division of concrete existences. Grote’s view (Aristotle, i. 108) that Aristotle drew up his list by examining various popular propositions, and throwing the different predicates into genera, “according as they stood in different logical relation to the subject,” has no foundation. The relation of the predicate category to the subject is not entirely a logical one; it is a relation of real existence, and wants the essential marks of the propositional form. The logical relations of tò õv are provided for otherwise than by the categories.

Aristotle has given no intimation of the course of thought by which he was led to his tenfold arrangement, and it seems hopeless to discover it. Trendelenburg in various essays has worked out the idea that the root of the matter is to be found in grammatical considerations, that the categories originated from investigations into grammatical functions, and that a correspondence will be found to obtain between categories and parts of speech. Thus, Substance corresponds to noun substantive, Quantity and Quality to the adjective, Relation partly to the comparative degree and perhaps to the preposition, When and Where to the adverbs of time and place, Action to the active, Passion to the passive of the verb, Position (κεισ0αι) to the intransitive verb, εχειv to the peculiar Greek perfect. That there should be a very close correspondence between the categories and grammatical elements is by no means surprising; that the one were deduced from the other is both philosophically and historically improbable. Reference to the detailed criticisms of Trendelenburg by Ritter, Bonitz, and Zeller will be sufficient.

Aristotle has also left us in doubt on another point. Why should there be only ten categories î and why should these be the ten! Kant and Hegel, it is well known, signalize as the great defect in the Aristotelian categories the want of a principle, and yet some of Aristotle’s expressions would warrant the inference that he had a principle, and that he thought his arrangement exhaustive. The leading idea of all later attempts at reduction to unity of principle, the division into substance and accident, was undoubtedly not overlooked by Aristotle, and Brentano has collected with great diligence passages which indicate how the complete list might have been deduced from this primary distinction. His tabular arrangements (pp. 175, 177) are particularly deserving of attention. The results, however, are hardly beyond the reach of doubt.

There was no fundamental change in the doctrine of the categories from the time of Aristotle to that of Kant, and only two proposed re-classifications are of such importance as to require notice. The Stoics adopted a fivefold arrangement of highest classes, γενικότατα. Tò õv or τi, Being, or somewhat in general, was subdivided into υποκείμενα or subjects, ποια or qualities in general, which give definiteness to the blank subject, πώς εχovτα, modes which further determine the subject, and. πρός τι πώς εχovτα, definite relative modes. These categories are so related that each involves the existence of one higher than itself, thus there cannot be a πρός τι πώς εχov which does not rest upon or imply a πώς eχov, but πώς εχov is impossible without ποιόν, which only exists in υποκείμενον, a form or phase of τδ õv.

Plotinus, after a lengthy critique of Aristotle’s categories sets out a twofold list. To ¢v, ιdvησ ∣ s, στάσιν, ταυτότης, iτepoτη<i are the primitive categories (πρώτα γivη) of the intelligible sphere. Oυσια, πpos τι, ποιά, ττοσόν, κwησις are the categories of the sensible world. The return to the Platonic classification will not escape notice.

Modern philosophy, neglecting altogether the dry and tasteless treatment of the Aristotelian doctrine by scholastic writers, gave a new, a wider, and. deeper meaning to the categories. They now appear as ultimate or root notions, the metaphysical or thought elements, which give coherence and consistency to the material of knowledge, the necessary and universal relations which obtain among the particulars of experience. There was thus to some extent a return to Platonism, but in reality, as might easily be shown, the new interpretation was, with due allowance for difference in point of view, in strict harmony with the true doctrine of Aristotle. The modern theory dates in particular from the time of Kant, who may be said to have re-introduced the term into philosophy. Naturally there are some anticipations in earlier thinkers. The Substance, Attribute, and Mode of Cartesianism can hardly be classed among the categories; nor does Leibnitz’s chance suggestion of a fivefold arrangement into Substance, Quantity, Quality, Action and Passion,and Relations,demand any particular notice. Locke, too, has a classification into Substances, Modes, and Relations, but in it he has manifestly no intention of drawing up a table of categories. What in his system corresponds most nearly to the modern view of these elements is the division of kinds of real predication. In all judgments of knowledge we predicate either (1) Identity or Diversity, (2) Relation, (3) Co-existence, or necessary connection, or (4) Real existence. From this the transition was easy to Hume’s important classification of philosophical relations into those of Resemblance, Identity, Time and Place, Quantity or Number, Quality, Contrariety, Cause and Effect.

These attempts at an exhaustive distribution of the necessary relations of all objects of knowledge indicate the direction taken by modern thought, before it received its complete expression from Kant.

The doctrine of the categories is the very kernel of the Kantian system, and, through it, of later German philosophy. To explain it fully would be to write the history of that philosophy. The categories are called by Kant Root-notions of the Understanding (Stammbegriffe des Verstandes), and are briefly the specific forms of the a priori or formal element in rational cognition. It is this distinction of matter and form in knowledge that marks off the Kantian from the Aristotelian doctrine. To Kant knowledge was only possible as the synthesis of the material or a posteriori with the formal or a priori. The material to which a priori forms of the understanding were applied was the sensuous content of the pure intuitions, Time and Space. This content could not be known by sense, but only by intellectual function. But the understanding in the process of knowledge makes use of the universal form of synthesis, the judgment; intellectual function is essentially of the nature of judgment or the reduction of a manifold to unity through a conception. The specific or type forms of such function will, therefore, be expressed in judgments; and a complete classification of the forms of judgments is the key by which one may hope to discover the system of categories. Such a list of judgments Kant thought he found in ordinary logic, and from it he drew up his well-known scheme of the twelve categories. These forms are the determinations of all objects of experience, for it is only through them that the manifold of sense can be reduced to the unity of consciousness, and thereby constituted experience. They are α priori conditions, subjective in one sense, but objective as being universal, necessary, and constitutive of experience.

The table of logical judgments with corresponding categories is as follows :— [table]

Kant, it is well-known, criticises Aristotle severely for having drawn up his categories without a principle, and claims to have disclosed the only possible method by which an exhaustive classification might be obtained. What he criticized in Aristotle is brought against his own procedure by the later German thinkers, particularly Fichte and Hegel. And in point of fact it cannot be denied that Kant has allowed too much completeness to the ordinary logical distribution of propositions; he has given no proof that in these forms are contained all species of synthesis, and in consequence he has failed to show that in the categories, or pure conceptions, are contained all the modes of a priori synthesis. Further, his principle has so far the unity he claimed for it, the unity of a single function, but the specific forms in which such unity manifests itself are not themselves accounted for by this principle. Kant himself hints more than once at the possibility of a completely rational system of the categories, at an evolution from one single movement of thought, and in his Remarks on the Table of the Categories gave a pregnant hint as to the method to be employed. From any complete realization of this suggestion Kant, however, was precluded by one portion of his theory. The categories, although the necessary conditions under which alone an object of experience can be thrown, are merely forms of the mind’s own activity; they apply only to sensuous and consequently subjective material. Outside of and beyond them lies the thing-in-itself, the blankest and emptiest of abstractions, which yet to Kant represented the ultimately real. This subjectivism was a distinct hiatus in the Kantian system, and against it principally Fichte and Hegel directed criticism. It was manifest that at the root of the whole system of categories there lay the synthetizing unity of self-consciousness, and it was upon this unity that Fichte fixed as giving the possibility of a more complete and rigorous deduction of the pure notions of the understanding. Without the act of the Ego, whereby it is self-conscious, there could be no knowledge, and this primitive act or function must be, he saw, the position or affirmation of itself by the Ego. The first principle then must be that the...