287. Common Essence and Individualized Essence (cf. 43). -- The Universals controversy was regarded as settled in the thirteenth century: scholastics unanimously accepted the solution arrived at towards the close of the twelfth. "The individual is the real substance, the universal reaches its fully developed form only through a subjective, elaboration of the mind." The most exacting dialecticians merely reproduce these stereotyped scholastic teachings; even Duns Scotus takes no exception to them. But no one is so precise and accurate in these delicate points of doctrine as the Angelic Doctor. It is as a tribute to his marvellously clear exposition of the doctrine, and not as claiming for him the credit of discovering it, that posterity has called moderate realism by the name of Thomistic realism (137). Of all the solutions of the Universals problem, it is the one that fits in best with the whole scholastic system.

Appropriating a formula that was current in the schools, St. Thomas thus gives expression to the doctrine of Albert the Great and Avicenna^{1} on the relation of the individual to the universal: The reality of any essence or thing may be considered in three states or stages: ANTE REM, IN RE, POST REM. The Universals ANTE REM are described and dealt with in the theory of Exemplarism with an Augustinian freedom of fancy which borders on the erroneous system of Avicenna. The Universals IN RE confront us with the physical side of the problem: the separate subsistence of individual things and the principle of their individuation.^{2} The Universals POST REM involve that subjective elaboration to which the mind submits all essences when it considers them apart from their individualizing conditions. Formally (formaliter) the universal exists only in the mind, but it has its foundation (fundamentaliter) in things.^{3}

Apart from the fourteenth-century terminists who denied the real, extramental validity of our universal presentations, and who thus betrayed the first symptoms of scholastic decadence, all agreed in recognizing a distinction -- in every created substance -- between the essential determinations that are similar in all the representatives of a species, and the individualizing determinations that differentiate these representatives from one another. The former are to the latter as determinable to determinant, as potency to act.

What is the nature of this distinction? In St. Thomas's view the concepts of specific essence and of individual essence correspond to different constitutive realities in the thing ("distinctio realis"). Others regard the diversity in the case as a mere logical distinction ("distinctio rationis"). Duns Scotus introduces here a "distinctio formalis a parte rei" (329). But none dare repeat the audacious language of Gilbert de la Porrée (176).

But another question arose, one that was much debated in the thirteenth century: What is the principle of individuation? In other words, if we are to reconcile the fixity and similarity of essences with the marvellous variety of their individuations, the question arises: how comes it that there are numerous individuals in one and the same species? Here is a scholastic controversy par excellence, presupposing as it does, at least up to a certain point, the peripatetic solution of the Universals problem. The medieval philosophers all admit that the basis of individuation ought to be essential and intrinsic; but they take divergent views on the question whether it is the matter or the form or the union of both principles that necessitates the individuation of things.

We find the Aristotelian system in St. Thomas, but so amplified and developed that the traditional portion is well-nigh imperceptible among the many innovations. Aristotle had shown why the form, being an indivisible principle, is incapable of multiplying itself, but he left the individualizing functions of the matter in obscurity. These St. Thomas analyzed, teaching clearly that the principle of individuation is not the matter in a state of absolute indeterminateness -- as some clumsy exponents of Thomism have represented, thus exposing the system to the charge of inconsistency -- but "materia signata," that is, the primal matter endowed with an intrinsic aptitude for occupying certain dimensions of space.^{4} As the process of natural change is conditioned by the presence of due proportions between the form and the dispositions of the matter, it follows that if natural agencies effect a change in these dispositions they will thereby bring about the introduction of a new form. And in this sense, the primal matter of any body in Nature becomes in the process of natural change the individualizing principle of the type or species into which that body passes.

From all this we see that it is only in the corporeal world the question of individuation can have any meaning for St. Thomas. More logical even than the Stagirite,^{5} he teaches that in the world of "separated" forms each individual is a complete species. To understand his teaching about the heavenly bodies, which, though composed of matter and form, are each unique of its kind, we must consult the general principles of scholastic physics (295).

{1} Cf. 217. These formulae go back at least to the time of Proclus. See his treatise In Euclidis Elementa, Prol. ii., p. 51, ed. Friedlein (Lipsiae, 1873): kata gar tautas oimai tas triplas hupostaseis heurêsomen ta men pro pollôn, ta de en tois pollois, ta de kata tên pros auta schesin kai katêgorian, huphistamena. And higher: en tois kath hekasta, . . . pro tôn pollôn . . . apo tôn pollôn.

{2} St. Thomas thus formulates the fundamental error of exaggerated realism, already at that time hopelessly discredited: "Credidit (Plato) quod forma cogniti ex necessitate sit in cognoscenti eo modo quo est in cognito, et ideo existimavit quod opporteret res intellectas hoc modo in seipsis subsistere, scilicet immaterialiter et immobiliter" (S. Theol., I^a, q. 84, art. I).

{3} In Lib. Sent. I., d. 19, q. 5, a. 1,

{4} Opusc. De Principio Individuationis. Same theory in Albert the Great, coloured by the doctrine of the "rationes seminales".

{5} Cf. ZELLER, Die Philos. d. Griechen, ii., 2, p. 339, n. 3.