Quality

QUALITY. - Q. (ποιότης) means, in a generic sense, mode of being. The universe, material and spiritual, not only presents a multiplicity of entities (v. PLURALISM), but also various and changing aspects, determinations, perfections (colors, sounds, weight, hardness..., thoughts, affections, virtues...), to which the generic term q. can refer.

In opposition to the atomists, who confined themselves to the consideration of quantitative elements, Anaxagoras (v.) and Empedocles (v.) introduced the concept of q. into the explanation of phenomena. Plato treats q. as a fundamental idea (Theaet., 182 ff.); Aristotle considers it as the third of the supreme genera of being

(Met., V, 7, 1017 a 25-30; I, 8, 8 b 25). St. Thomas (Sum. Theol., 1ª, q. 28, a. 2; 1ª-2ª, q. 49, a. 2) defines q. as «modus essendi», «dispositio substantiae» and distinguishes essential q., the determination of substantial being itself by form (v.), and accidental q., or q. properly so called, a further determination of substance, really distinct from it (v. ACCIDENT; SUBSTANCE). Accidental q. is classified according to a fourfold distinction: 1) as a direct determination of substance: habits (v.) and dispositions (knowledge, virtue, vice, health, illness, supernatural virtue, Grace...); 2) as a principle of operation or activity: operative powers or faculties (senses, intellect, will...); 3) as a principle of alteration or passivity: sensible q.; 4) as determinations of quantity: form and figure. Descartes (v.) defines q. as a property of substance; it is twofold, thought, or the q. of spirit, and quantity, or the q. of body (Princ. philos., I, n. 56 and 63; ed. Ch. Adam-P. Tannery, VIII, 26 ff.). In Kant q. is one of the modes of judging to which belong the categories of reality, negation and limitation (Critique of Pure Reason, Ital. trans. by G. Gentile and G. Lombardo-Radice, I, Bari 1919, p. 109 ff.). Hegel posits q. as a moment in the dialectical development of the idea (v.); it is opposed to indeterminate being as the first and immediate determination and is divided again into pure being, determinate being and being for itself (The Science of Logic, Ital. trans. by A. Moni, I, Bari 1924, p. 72 ff.). In Bergson (L'évolution créatrice, Paris 1940, p. 300 ff.) q. is a stable perceptual vision of change and real becoming, while Boutroux (v.) affirms the qualitative element as essential to all reality (De la contingence des lois de la nature, Paris 1902, p. 29 ff.).

Sensible q. - In philosophy, the problem of q. is referred particularly to sensible q. Indian thought had already affirmed their subjectivity; among the Greeks, first the Eleatics and then the atomists consider them as deceptive and subjective appearances; Protagoras and Aristippus point out their relativity; Plato declares them the object of sensation and not of science (Theaet., 186). Aristotle (De an., II, 6-12) and then Scholasticism defend the objectivity of sensible q., distinguished into «primary» (hot and cold, dry and moist) and «secondary» or derived. In the period of the decadence of Scholasticism (v.) there was no little discussion concerning the «qualitates occultae», postulated to explain phenomena and natural forces: against them and against all sensible q. Galileo (v.), Descartes and Locke (v.) pronounced. Mechanism (v.), resuming the position of ancient atomism (v.), denies the existence of q. in the physical world, reducing all material reality to quantity and local motion alone and regarding qualitative varieties as purely subjective reactions of the senses. The problem has a properly critical-epistemological aspect (for which v. PERCEPTIONISM) and a physical-cosmological aspect, which consists in determining the nature and properties of the various sensible q. and the laws that govern them, and is treated in the various parts of physics. In general modern physics, especially through the energetic reaction (Duhem, Ostwald) against the mechanism of classical physics and the theories of relativity and quanta (v.), recognizes the irreducibility of q. to quantity and local motion alone and the necessity of qualitative elements for the explanation of physical reality: such are the various forms of energy (v.), especially electromagnetic and gravitational. It is a merit of mechanism to have brought to light the necessity, fundamental in all modern physics, of subjecting q. as well to a rigorous process of measurement and mathematical calculation. The quantitative method, however, is not opposed to the affirmation of sensible q. and, even according to the principles of Scholastic philosophy, can be introduced into the study of q., insofar as these too have a quantity, the «intensio» or «quantitas virtutis», measurable by the quantitative effects it produces: «nam quantitas virtutis secundum effectus mensurari solet» (St. Thomas, Comp. theol., cap. 216); thus from the expansion of mercury in a thermometer one measures the intensity or degree of the temperature of a body. On the subjective or psychological element corresponding to sensible q. and on its measurement, the fruitful researches of modern psychology are well known, in particular those of Fechner, Weber, Paulsen, Wundt (v. these entries, and also SENSATION).

The problem of the intensity and the increase of q. received particular consideration in Scholasticism, because of its theological repercussions in the question of the increase of Grace, charity and supernatural virtues. There are, substantially, two main explanations proposed: the first, defended by Scotus (Commentaria ad I librum Magistri sent., dist. XVII, qq. 4, 5, 6; I, Quaracchi 1912, p. 834 ff.) and by Suárez (Disp. metaph., disp. 46, ed. Vivès, XXVI, Paris 1861, p. 753 ff.), explains the increase of q. by the addition (additio) of new entities, just as weight can be increased by the addition of new weights; the other, upheld by St. Thomas (Sum. Theol., 1a-2ae, q. 52, a. 1 and 2; 2a-2ae, q. 24, a. 4-7; De virt., q. 1, a. 11), explains the increase «per hoc quod subiectum magis vel minus perfecte participat unam et eandem formam», that is, insofar as one and the same form actuates ever more perfectly the potential capacity of the subject, under the action of an external agent cause or through the repetition of acts. In reality the Scotist-Suárezian opinion explains only the increase of the «quantitas per accidens» of q. (e.g., to have a greater quantity of heat it suffices to add new bodies having the same degree of temperature), whereas to explain the increase of intensity or «quantitas intensiva» (e.g., the increase of temperature) it is necessary to have recourse to the second explanation.

Filippo Selvaggi