SUBSTANCE. — It may indicate either effective and concrete reality, that is, the singular (the “first substance” of Aristotelian terminology), essence (v.), both in its metaphysical structure and in its notional and logical content (“second substance”: cf. Cat., 5, 2 a 11 ff.), or also the particular “this” (τόδε τι) and the “what it is” (τὸ τί ἔστιν: Met., VIII, 1, 1028 a 11).
By s. is therefore understood the “principal” mode of being, and hence the first category of reality, the foundation, cause, and substrate of accidents (v.), whether proper or common. Accordingly, the meaning of “subject” or “substrate” (τὸ ὑποκείμενο) varies according to the number of modes of s. itself in the logical or real order, namely: 1) insofar as s. is the principal reality that sustains accidents and is then called, in the strict sense, τὸ εἶδος or ἡ μορφή (Met., VIII, 3, 1028 b 34); 2) the same ultimate subject, or prime matter (πρώτη ὕλη); 3) in the logical order, the universal (τὸ καθόλου), which is the species and the genus. Insofar as it indicates the consistency of being, 4) s. is the reality in act (οὐσία), which may be understood as essence complete in itself (in the corporeal entity, the synthesis of matter and form, τὸ σύνολον: Met., VIII, 3, 1033 b 1), or finally 5) singular subsistence (τό δε τι), which is substance in the fullest sense, in which the real is actualized in its various forms.
In the anti-Platonic polemic (Met., I and VII-VIII), Aristotle maintained that s. must be identified in sensible reality, with which experience places us in continuous contact and on which we necessarily always depend, both for knowing and for acting. The Platonic problem, therefore, of the “communion of genera” (συνωνία τῶν γενῶν), which in Plato always remained unresolved, becomes in Aristotelianism the problem of the “duality” of matter and form in essence, and definition (v.). But the duality of principles does not destroy—indeed, it guarantees—the unity of the real on the one hand and of the concept on the other. In reality, this unity is guaranteed by the unity of form, and in definition by the specific difference that constitutes essence and corresponds to form. In this way Aristotelianism closes off the process to infinity (which instead remains open in Platonic dialectic), because form is immanent in the singular sensible thing; hence informed matter and the form actualizing matter coincide in the unity of the entity: ἡ ἐσκάτη ὕλη καὶ ἡ μορφή ταύτῳ καὶ ἕν, καὶ δυνάμει, τὸ δ'ἐνεργεία (Met., VIII, 5, 1045 b 18). Matter and form, therefore, in the structure of substance (and of definition) do not stand on an equal footing; rather, form dominates matter and actualizes it at its ontological level: « Unumquodque ponitur in sua specie per formam... » (s. Tommaso, In VII Met., lect. 11, n. 1531: cf. Sum. Theol., 1ᵃ, q. 85, a. 1 ad 2). In the metaphysical structure of corporeal essence, therefore, form and matter (and soul and body) are like the concave and the convex, and not two elements requiring an “intermediate principle” of connection. The latter conception betrays a dualism that conceives the two principles separately and, ultimately, a failure to understand the metaphysics of act and potency: « Ultima materia, quae scilicet est appropriata ad formam, et ipsa forma, sunt idem. Aliud enim eorum est sicut potentia, aliud sicut actus... Et sic non oportet ea uniri per aliquod vinculum » (In VIII Met., lect. 5, n. 1767). The theory of the “substantial bond” was developed by Leibniz and his school, but its first explicit indications appear in Suárez, from whom Leibniz himself in all probability drew his inspiration (as Ch. Boehm has demonstrated [Le vinculum substantiel chez Leibniz, Paris 1938], correcting on this point the thesis of M. Blondel [Une énigme historique: Le « vinculum substantiale » d'après Leibniz et l'ébauche d'un réalisme supérieur, ibid. 1930: it is the French translation of the 1893 Latin thesis]). Leibniz (v.), for his part, developed a theory of s. as a “monad” complete in itself, so that every s., even a material one, is a world apart; what s. Tommaso says of the angels, that each is a species apart, is, according to Leibniz, « est de toutes les substances... De plus, toute substance est comme un monde entier et comme un miroir de Dieu ou bien de tout l'univers, qu'elle exprime chacune à sa façon » (Discours de metaphysique, § IX; ed. H. Lestienne, Paris 1929, p. 37). More restrained in its theoretical demands, Thomistic metaphysics elaborated the concept of s. according to the principle of the “emergence of act” (Met., IX, 8, 1049 b 5; cf. De an., II, 4, 415 a 18). Material s. obtains its actuality and ontological consistency from form: (Quod., I, q. IV, a. 6; cf. Arist., De an., II, 4, 415 b 13: τὸ γὰρ αἰτῶν τοῦ εἶναι πᾶσι ἡ ὁδοία). Consequently, spiritual substances, which are simple forms without matter, are more perfect and consistent than material substances and are therefore called “subsistent” or separate forms; as such, they are closer to God, who is pure subsistent being (cf. De spir. creat., a. 1). Thus, in the ontological structure of s., as “subsistence” (v.) increases, the character of subject or receptivity with respect to accidents diminishes; in spiritual substances these are reduced to the sole qualities and actualizations of the intellect and will, while God is pure act, the fullness of perfection in absolute simplicity.
The disruption of the balance of the Aristotelian metaphysics of act and potency, already accomplished in Suárez, who does not accept the Thomistic concept of potency, appears in Leibniz as the elimination of potency as receptivity in order to intensify potency as virtuality and activity. Spinoza (v.), “s.” instead expresses absolute self-sufficiency, which entails the metaphysical unity of the real in the identity of modes and attributes (extension and thought, intellect and will): « Per substantiam intelligo id quod in se est et per se concipitur: hoc est id cuius conceptus non indiget conceptu alterius rei, a quo formari debeat » (Ethica, ed. Gentile, Bari 1933, p. 3). At this point Hegel unified Leibnizian dynamism and Spinozian unity in the conception of reality as “process” (cf. Phán. d. Geistes, Vorrede, ed. J. Hoffmeister, Leipzig 1937, p. 43).
English empiricism, on the other hand—by way of reaction against rationalism—reduced s. to the function of “substrate” and thereby brought about the dissolution of the very concept of substance. Proceeding from the nominalist principle that the primary value of reality belongs to immediate perception and that “ideas” are nothing but the mental “residue” of sensations, Locke maintains that substances are not properly knowable, nor is it possible to form a precise notion of them (cf. Essay, I, 4, 18; ed. J. A. St. John, I, London 1854, p. 196 ff.). Our knowledge of s. is therefore reduced to an entirely vague “complex idea” of some unknown support of accidents (ibid., II, 23, 3; ed. cit., I, p. 424), and in concrete terms to an “interweaving (complication) or collection of those diverse simple ideas of sensible qualities which are usually found united in things called a horse or a stone” (ibid., p. 425). This applies not only to material substances but also to spiritual substances and to our own soul or mind (ibid.).
To escape the deadlock, BERGER, ELIE (v.) denied the concept of material substance and thereby the notion of substrate, the Lockean theory of “complex ideas,” and the distinction between primary (v.) and secondary qualities: the existence of things is identified with their being perceived (esse est percipi); consequently, the concept of material substance or substratum is contradictory (Principles, §§ 5-23). The only substance is the soul, which attests itself as the “cause” of the feelings, ideas, and notions that we continually experience or produce within ourselves (ibid., § 25). Finally, Hume (v.), proceeding from Berkeley’s reduction of spiritual substance to the concept of the “cause” of its own modifications, cause (v.) has no foundation, either a priori or a posteriori, in our knowledge, because we lack the corresponding impression. Cause, and with it substance, is reduced to a natural conviction (belief), to an instinctive feeling whose origin we do not know (Treatise on human nature, part 1, section 7; part 4, section 3; ed. Selby-Biggs, Oxford 1928, pp. 17 ff., 219 ff.; see also Appendix, p. 633).
In the metaphysics of immanence, substance is either absorbed without remainder into the becoming of the Whole of reason or universal history (pantheistic monism), or is wholly resolved into the remainder itself, which is the singular fact of becoming (phenomenalism); in the metaphysics of transcendence, on the other hand, substance has an absolute foundation in the “form” that structures the individual in time and space, and form in turn is grounded in the divine intellect, from which every essence derives its first origin.