ABSTRACT, ABSTRACTION. - 1. In general, "a." is the qualification of mental contents, the universal ideas or concepts (v.), as opposed to things existing per se in reality, that is, "concrete." Within the same ideal sphere, the reflected or logical universal (animalitas, humanitas... = genus and species...) can be called "a." in relation to the direct and metaphysical universal (animal, homo), insofar as the one expresses the mode of belonging and predication of a nature and the other the real content of that nature according to the mode of being it has in reality. Finally, in the real sphere, "a." is the qualification of substances that are entirely free from commerce with matter, such as God and the pure spirits: a notion already present in Plato and Aristotle and which had particular diffusion in Neoplatonic metaphysics (transcendence of the One and the Good).
In Hegel, on the contrary, "a." is the individual as such, which is the subject of perception ("this, here, now"), insofar as it is considered in itself outside the dialectical movement and therefore unreal; while "concrete" is the qualification of self-consciousness in that ultimate and complete form which is spirit, absolute creative freedom of itself and of its modes, corresponding to the categories (Hegel, Vorlesungen über die Geschichte der Philosophie, Leiden 1908, Italian trans., I, Florence 1930, p. 34 ff.).
In actualism (v.) the concrete, which is spirit, is conceived as the indefinite movement of an act never made that always makes itself and becomes: there is no pure thesis nor pure antithesis, as Hegel wanted, there is no being and not-being, but the synthesis, that single act which we are, thought (G. Gentile, La riforma della dialettica hegeliana, 2nd ed., Messina 1923, p. 207). In existentialism (v.) the concrete returns to being the individual, the existing person, and "a." the thought object.
2. For Plato, the "Ideas" were also "real instructions," that is, the universal forms and species that subsisted per se "separated" from the material substances of which they were the exemplars. The existence of particulars was explained by Plato through a "participation" in the Idea, and correlatively the valid knowledge that the soul seeks in science through a direct "participation" in those same subsisting intelligibles. For Aristotle, on the other hand, natural substances imply as their own constitutive element, together with form, also matter; they are "synola" of matter and form where form is not understood except as act and first perfection of a matter because it cannot exist except in it: the definition must therefore refer both to matter and to form (Metaph., VI, 1, 1025 b, 31-1026 a, 5; v. ibid., VIII, 5, 1030 b, 14 ff.; De Anima, III, 4, 429 b, 10 ff.). From this situation came a double consequence: a) the essence and form insofar as it is united to matter is not per se intelligible, but manifests itself only through sensible qualities; b) the human soul, substantial form of the body, is pure potency in the order of knowing: it therefore does not have the intelligibles congenitally in itself nor does it "participate" directly in them. Just as essences are potentially intelligible in sensible qualities, so the soul can unite itself to them in knowledge by starting from sensible manifestations: the process that effects this passage from the concrete sensible to the abstract intelligible is called "abstraction."
Every passage from potency to act requires a principle in act that can move to act the principle that is in potency. In the soul there must therefore be two principles of understanding; the one active (the agent intellect) a productive principle of the intelligible from the sensible, the other passive
(the possible intellect) receptive of the abstract intelligible (De Anima, III, 5, 430 a, 10 ff.; Sum. Theol., 1ª, q. 79, a. 1-4). The entire process of abstraction is accomplished in three stages: 1) the preparation of the "phantasms" or sensory representations by the external and internal senses, in particular by the cogitative power (v.) and memory (v.; C. Gent., II, 60); 2) the production, by the work of the agent intellect, of the intelligible form ("impressed species") from the sensible forms of the phantasms, which comes to actualize the possible intellect; 3) the assimilation by this latter of the essence thus abstracted and presented in the intelligible species, and the production — at a second moment — of an immanent term of intellection, which is the "verbum" or inner word (species or intentio intellecta; C. Gent., I, 53; IV, 11). The phase in which abstraction is properly actualized is the second, insofar as it is in it that the passage from sensible contents to intelligible ones is effected. St. Thomas explains the possibility of this passage, subjectively, insofar as both sense and intellect belong to the same soul and derive from it in relations of mutual dependence (Sum. Theol., 1ª, q. 77, entire); objectively, through the complementarity between the nature of the soul and the content of the phantasm: "Anima intellectiva est quidem actu immaterialis sed est in potentia ad determinatas species rerum. Phantasmata autem e converso sunt quidem actu similitudines specierum quarundam, sed sunt potentia immateriales. Unde nihil prohibet unam et eandem animam, in quantum est immaterialis in actu, habere aliquam virtutem, per quam faciat immaterialia in actu, abstrahendo a conditionibus individualis materiae (quae quidem virtut dicitur intellectus agens), et aliam virtutem receptivam huiusmodi specierum quae dicitur intellectus possibilis, in quantum est in potentia ad huiusmodi species" (Sum. Theol., 1ª, q. 79, a. 4, ad 4). The collaboration between agent intellect and phantasm occurs in a double order of causality: first, insofar as the phantasm presents the "matter" of knowing, the object in its concreteness which must pass into universality through the efficacy of the illumination of the agent intellect; and then insofar as the phantasms, thus illuminated, become the "instrumental cause," through which the agent intellect impresses in the possible intellect the species of the intelligible or impressed species (Quodlib., VIII, 3; Sum. Theol., 1ª, q. 85, a. 1, ad 4). A collaboration that is at once the reflection and the sign of the substantial union of soul and body, and which for St. Thomas expresses the indispensable condition of all our knowing; at its first arising no less than for the use of knowledge already acquired, the intellect needs to refer to phantasms ("conversio ad phantasmata"), it does not "think the intelligible essences except in phantasms" (De Anima, III, 7, 431 b; Sum. Theol., q. 84, a. 6-7). The mode, however, of this reference or conversion to phantasms, although it is uniform in the initial knowledge of simple apprehension, is different for the terminal knowledge of the different orders of constituted sciences, which involve affirmations and negations and therefore explicit attributions about the mode of being of things in themselves.
3. Insofar as it includes pronouncing on being with affirmations and negations, "a." belongs to judgment, is subject to truth or falsity according as its attributions are conformable or not to reality. The "a." of simple apprehension is not subject to this, since it prescinds from every attribution and limits itself to presenting a content, and for it the Aristotelian axiom holds: "Abstrahentium non est mendacium" (Phys., II, 2, 193 b, 35).
There are two principal forms of abstraction: the one when the whole is abstracted from the parts and a universal from the particular, as animal from man; the other when the form is abstracted from matter (Sum. Theol., 1ª, q. 40, a. 3). To the first belong, under different titles, the first confused cognitions and the notions of logical abstraction; to the second, on the other hand, belong the fields of the sciences (Cajetan coined the terms abstraction "total" and abstraction "formal"). For St. Thomas not every abstraction can be called a "praecisio" or separation from the object of departure: such is the abstraction of the whole from the parts and of the singular from the universal, not that of form from matter, unlike those Scholastics who more or less identify them (nominalism, Suárez). The divergence arose from the fact that for these Scholastics, as for the Augustinians, the first object of the intellect is the singular substance and not the universal nature, or rather the most indeterminate notion of being, as the Angelic Doctor holds. The reason for the divergence is to be sought in the different metaphysical conception of act and potency, of matter and form: the anti-Thomists, since they attribute to matter and potency a certain act, both formal and entitative, make the singular individual the object — indeed the first object — of direct intellection; therefore they conceive abstraction as a separation or "praecisio" that the intellect subsequently performs within that global content.
Abstraction is opposed to "intuition" (v.). In man it is to the (external) senses that intuitive knowledge belongs, insofar as in them sensible qualities become present in the concreteness and singularity that they have in things. Therefore St. Thomas rejected the "agent sense," advanced by certain Averroists, and was thus able to secure the direct contact of human knowledge with external reality (Sum. Theol., 1ª, q. 79, a. 3, ad 1). In a less rigorous sense, the immediate apprehension of the first notions and first principles may be called "intuition," and in this sense certain modern Thomists speak of an "abstractive intuition," even if the term seems almost contradictory. The abstraction that leads to the first notions and first judgments, since it cannot presuppose other knowledge in the soul, is accomplished in the form of an "induction" (v.) which, however, is not scientific induction, but a process "sui generis" (Post. Anal., II, 19, 99 b, 23 ff.; Metaph., I, 1, 980 b, 28 ff.).
In a moral and mystical sense, abstraction entails liberation from the conditions and inclinations of sensibility and can take different forms, from those acquired through the exercise of temperance and ascetic detachment to those caused by a superior being and which are called "alienations" and "raptures," and can come as much from divine virtue as from diabolical virtue, and at times also from particular bodily dispositions of the subject (Sum. Theol., 2ª-2ª, q. 15, a. 3; q. 175, a. 1). The abstraction that is caused by God constitutes the state of "ecstasy" (v.).
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Cornelio Fabro