[24] This is the just remark of Trendelenburg, Kategorienlehre, p. 217.
With these details, however, the question between Realism and its counter-theory (whether Conceptualism or Nominalism) is not materially concerned. The standard against Realism was raised by Aristotle in the First Category, when he proclaimed the Hoc Aliquid to be the only complete Ens, and the Universal to exist only along with it as a predicate, being nothing in itself apart; and when he enumerated Quality as one among the predicates, and nothing beyond. In the Platonic Realism (Phædon, Timæus, Parmenides) what Aristotle called Quality was the highest and most incontestable among all Substances — the Good, the Beautiful, the Just, &c.; what Aristotle called Second Substance was also Substance in the Platonic Realism, though not so incontestably; but what Aristotle called First Substance was in the Platonic Realism no Substance at all, but only one among a multitude of confused and transient shadows. It is in the First and Third Categories that the capital antithesis of Aristotle against the Platonic Realism is contained. As far as that antithesis is concerned, it matters little whether the aggregate of predicates be subdivided under nine general heads (Categories) or under three.
In the century succeeding Aristotle, the Stoic philosophers altered his Categories, and drew up a new list of their own, containing only four distinct heads instead of ten. We have no record or explanation of the Stoic Categories from any of their authors; so that we are compelled to accept the list on secondary authority, from the comments of critics, mostly opponents. But, as far as we can make out, they retained in their First Category the capital feature of Aristotle’s First Category — the primacy of the First Substance or Hoc Aliquid and its exclusive privilege of imparting reality to all the other Categories. Indeed, the Stoics seem not only to have retained this characteristic, but to have exaggerated it. They did not recognize so close an approach of the Universal to the Particular, as is implied by giving to it a second place in the same Category, and calling it Second Substance. The First Category of the Stoics (Something or Subject) included only particular substances; all Universals were by them ranked in the other Categories, being regarded as negations of substances, and designated by the term Non-Somethings — Non-Substances.[25]
[25] Prantl, Gesch. der Logik, I. vi. p. 420: οὔτινα τἀκοινὰ παρ’ αὐτοῖς λέγεται. &c.
The Neo-Platonist Plotinus, in the third century after the Christian era, agreed with the Stoics (though looking from the opposite point of view) in disapproving Aristotle’s arrangement of Second Substance in the same Category with First Substance.[26] He criticizes at some length both the Aristotelian list of Categories, and the Stoic list; but he falls back into the Platonic and even the Parmenidean point of view. His capital distinction is between Cogitables and Sensibles. The Cogitables are in his view the most real (i.e. the Aristotelian Second Substance is more real than the First); among them the highest, Unum or Bonum, is the grand fountain and sovereign of all the rest. Plotinus thus departed altogether from the Aristotelian Categories, and revived the Platonic or Parmenidean Realism; yet not without some Aristotelian modifications. But it is remarkable that in this departure his devoted friend and scholar Porphyry did not follow him. Porphyry not only composed an Introduction to the Categories of Aristotle, but also vindicated them at great length, in a separate commentary, against the censures of Plotinus; Dexippus, Jamblichus, and Simplikius, followed in the same track.[27] Still, though Porphyry stood forward both as admirer and champion of the Aristotelian Categories, he did not consider that the question raised by the First Category of Aristotle against the Platonic Realism was finally decided. This is sufficiently proved by the three problems cited above out of the Introduction of Porphyry; where he proclaims it to be a deep and difficult enquiry, whether Genera and Species had not a real substantive existence apart from the individuals composing them. Aristotle, both in the Categories and in many other places, had declared his opinion distinctly in the negative against Plato; but Porphyry had not made up his mind between the two, though he insists, in language very Aristotelian, on the distinction between First and Second Substance.[28]
[26] Plotinus, Ennead. vi. 1, 2.
[27] Simplikius, Schol. in Aristotel. Categ. p. 40, a, b, Brandis.
[28] Prantl, Geschichte der Logik, I. xi. p. 634, n. 69. Upon this account Prantl finds Porphyry guilty of “empiricism in its extreme crudeness� — “jene äusserste Rohheit des Empirismus.�
Through the translations and manuals of Boëthius and others, the Categories of Aristotle were transmitted to the Latin Churchmen, and continued to be read even through the darkest ages, when the Analytica and the Topica were unknown or neglected. The Aristotelian discrimination between First and Second Substance was thus always kept in sight, and Boëthius treated it much in the same manner as Porphyry had done before him.[29] Alcuin, Rhabanus Maurus, and Eric of Auxerre,[30] in the eighth and ninth centuries, repeated what they found in Boëthius, and upheld the Aristotelian tradition unimpaired. But Scotus Erigena (d. 880 A.D.) took an entirely opposite view, and reverted to the Platonic traditions, though with a large admixture of Aristotelian ideas. He was a Christian Platonist, blending the transcendentalism of Plato and Plotinus with theological dogmatic influences (derived from the Pseudo-Dionysius Areopagita and others) and verging somewhat even towards Pantheism. Scotus Erigena revived the doctrine of Cogitable Universalia extra rem and ante rem. He declared express opposition to the arrangement of the First Aristotelian Category, whereby the individual was put first, in the character of subject; the Universal second, in the character only of predicate; complete reality belonging to the two in conjunction. Scotus maintained that the Cogitable or Incorporeal Universal was the first, the true and complete real; from whence the sensible individuals were secondary, incomplete, multiple, derivatives.[31] But, though he thus adopts and enforces the Platonic theory of Universals ante rem and extra rem, he does not think himself obliged to deny that Universals may be in re also.
[29] Prantl, Geschichte der Logik, I. xii. p. 685; Trendelenburg, Kategorienlehre, p. 245.