HYLEMORPHISM. - From ὅλη (matter) and μορφή (form), it indicates the philosophical theory, due to Plato and Aristotle, which holds that corporeal substance is composed of an indeterminate element (matter) and a determinate one (form).
The first Greek philosophy, with its attempts to explain becoming, prepared the way for hylomorphism. Against the mobilism of Heraclitus, Parmenides affirms immobility: "For being exists, while nothing is not" (frg. 6, 1-2); this being is immobile. For change is either from being or from non-being; but both are impossible, "for neither can being come to be (for it already is), nor can anything come to be from non-being; οὔτε γὰρ τὸ ὄν γίγνεσθαι (εἶναι γὰρ ἦδη), ἐκ τε μὴ ὄντος οὐδὲν ἂν γενέσθαι (Aristotle, Phys., I, 8, 191 a 30-31). Nothing, therefore, is born, nothing changes. This dilemma left its mark on later philosophers, who tried to break it. Empedocles and Anaxagoras explain cosmic becoming in a mechanistic way; so too Leucippus and Democritus, for whom "the full and the solid is being, the void is non-being," and therefore "being no more exists than non-being, since the full no more exists than the void" (id., Met., I, 4, 985 b 7-9). The parts of being (the full) are the atoms, indivisible (ἄτομος) and impassible (ἀπαθής) like the being of Parmenides, differing from one another in figure, order and position: their moving in the void and their mingling accounts for becoming (ibid., 985 b 5 ff.).
Plato explains the mutability of worldly things by a χώρα "difficult and obscure," almost "a receptacle (ὑποδοχήν) of what is generated, almost a nurse" (id., Tim., 49 a), which has in itself no form, but receives all forms, which are images of the immutable ideas. The body results from the union of the χώρα and an image of the ideas. Aristotle, having assumed the evident existence of becoming (Phys., I, 2, 185 a 13-14), observes: just as when a man becomes musical, the man who is the substrate remains, while the non-musical disappears (ibid., 7, 190 a 95 ff.), so in every change there is the substrate that remains, the privation of form, and the form: δῆλόν ἐστιν ὅτι δεῖ ὑποκείσθαι τι τοῖς ἐναντίοις καὶ τἀναντία δύο εἶναι (ibid., 191 a 4-5). With these concepts Aristotle proposes a first solution of the Parmenidean dilemma, later developed on the basis of the doctrine of potency and act (ibid., 8, 191 b 27-29). A reality becomes actually something in so far as it had a real capacity or subjective potency to become, hence between non-being in the total sense (μὴ ὄν) and being in act (ἐνεργείᾳ ὄν) there is being in potency (δυνάμει ὄν). Not from the μὴ ὄν nor from the ἐνεργείᾳ ὄν, but from the δυνάμει ὄν does change occur: "Since being is twofold, everything changes from being in potency to being in act...; from being everything becomes, that is, from being in potency, from non-being in act" (Met., XII, 2, 1069 b 15-20). Aristotle applies these notions to substantial becoming, which supposes an indeterminate substrate, the δυνάμει ὄν in the substantial order, called prime matter (ὕλη ἡ πρώτη, ibid., V, 6, 1017 a 5), the privation of determination (στέρησις) and the substantial determination, called form (μορφή): "In all changes between opposites, there is something that serves as their substrate... And similarly let it be said for substantial changes: there is something that is now in generation and now in corruption, now is a determinate substrate and now is according to privation" (ibid., VIII, 1, 1042 a 32-63). Corporeal substance is therefore composed of matter and form: γίγνεται πᾶν ἐκ τε τοῦ ὑποκειμένου καὶ τῆς μορφῆς (Phys., I, 7, 190 b 20). St. Thomas comments: "Omne quod fit, est et fit ex subiecto et forma... Et notandum est quod hic intendit inquirere principia non solum fiendi sed etiam essendi: unde signanter dicit: ex quibus primis [principiis] sunt et fiunt" (Phys., I, lect. 13; cf. Met., VIII, lect. 1, ed. M. R. Cathala, Turin 1915, pp. 488-89, n. 1689).
Prime matter is a totally indeterminate principle: "I call matter that which in itself is not a determinate thing, nor a quantity, nor any other of the determinations of being" (Met., VII, 3, 1029 a 20); "materia, secundum suam substantiam, est potentia ad esse substantiale" (St. Thomas, Phys., I, lect. 15). Substantial form, on the other hand, is the principle that confers the first specific being and ontological unity on the composite. Matter and form are therefore not beings (ens quod) but principles of being (ens quo). The form, moreover, does not exist prior to and independently of matter, but arises from the very potentiality of matter in the process of its becoming, "in quantum materia, quae est in potentia ad formam, fit actu sub forma, quod est facere compositum" (St. Thomas, In Met., VII, lect. 7, ed. cit., n. 1423).
Hylomorphism, understood in various ways by the Greeks, Arabs and Latins, and first clarified in its true sense by St. Thomas (cf. P. Hoenen, Cosmologia, 3rd ed., Rome 1945, p. 274), is instead misrepresented by Duns Scotus, who maintains that prime matter can exist separately (Op. Ox., I, II, dist. 12, q. 2, n. 3; VI, ed. L. Wadding, Lyon 1539, p. 682; cf. ibid., n. 4, p. 682). Similarly F. Suárez (Disp. Met., d. 13, s. 4-5). The notion of form as ens quo is not understood, nor consequently the "eductio formae e potentia materiae," by R. Descartes (Epist. ad Regium, ed. C. Adam and P. Tannery, Paris 1897-1910, III, pp. 502, 505-506), P. Gassendi (Physica, I, sect. 1, I, VII, cap. 3, Lyon 1658, p. 469), G. Leibniz (Essais de théodicée, I, nn. 87-89; VI, ed. C. I. Gerhardt, pp. 149-51), E. Zeller, Philosophie der Griechen, II, II, 4th ed., Berlin 1876, p. 347 ff.), and many others (cf. P. Hoenen, De origine formae materialis, Rome 1932). Various philosophical systems deny hylomorphism (mechanism, atomism, dynamism, positivism, phenomenalism, idealism, etc., v. these entries) for general metaphysical reasons.
Given the objective reality of extended bodies, not a few authors base hylomorphism on the Aristotelian argument from substantial change. Following the difficulties raised by scientific atomic theory, others attempt to derive hylomorphism from the fact that the body is a spatio-temporal reality, with energetic and inertial properties. The actual unity and potential multiplicity of the continuum, they maintain, cannot be adequately explained without admitting in corporeal substance a principle of unity and determination (form) and a principle of multiplicity and indetermination (prime matter; cf. St. Thomas, C. Gent., II, cap. 65; P. Descoqs, Essai critique sur l'hylémorphisme, Paris 1924, p. 237). An analogous argument is drawn from the consideration of corporeal existence, to which belong together unity and diffusion in time (cf. F. Renoirte, Éléments de critique des sciences et de cosmologie, Louvain 1947, p. 227). Finally hylomorphism is further confirmed by the twofold and opposite series of properties of corporeal substance: on the one hand quantity and energy, on the other quality and activity (electro-magnetic forces, etc.; cf. P. Descoqs, op. cit., p. 269 ff.). These last three considerations are connected with one another and can be regarded as a single foundation of hylomorphism, under different points of view, which complement one another. Other authors, taking as evident the principle that pure act is unique and infinite and is multiplied when it is participated in a potential subject, deduce from the fact that there exist several corporeal individuals of the same species that these bodies are composed of a participated substantial act and of a substantial potency that receives it (cf. St. Thomas, De spir. creat., a. 1, ad 9; Phys., VIII, lect. 2). The argument is much discussed, inasmuch as others maintain that the principle of participation is founded on hylomorphism.
Modern science seems to oppose hylomorphism, according to which matter is made up of particles, which some physical theories hold to be ontologically distinct and sometimes even spatially distant. On this point it is observed that if bodies were really to be understood as aggregates of particles (and therefore of distinct individualities), the hylomorphic theory can be referred to these. Indeed, it does not seem possible to admit, as some maintain (St. Albert the Great, P. Descoqs, M. Fatta, etc.), that the particles, while remaining unchanged, are taken up by a higher substantial form into a substantial metaphysical unity, nor that metaphysical unity can consist in physical discontinuity. But the activity of the living body strongly persuades us of its substantial unity, from which it follows that, both in the assimilation of food and in the destruction of the living being following death, substantial mutations are involved. This argues, in the elements taken up into the unity of the living being, and, by extension, in bodies in general, for the essential composition of matter and form.
In physics itself, if one sets aside theoretical constructions, observations on nuclei, atoms and crystals, understood in their concrete experimental value, indicate a heterogeneous particulate constitution (that is, with different properties in different parts) of matter, so that it is not imposed upon us to think of the particles in the compound as ontologically distinct individuals (cf. P. Hoenen, Cosmologia, p. 316 ff.); in the atom, in chemical compounds and also in crystals a heterogeneous continuity is therefore possible, which permits the ontological substantial unity of higher bodies. Moreover, the very recent physical theory of quantum mechanics, rejecting the intuitive notion of the corpuscle as a material point, rejects the mechanical theories of discontinuous matter, that is: « it rejects the presupposition, inherent in all previous theories, that atoms, photons and the other entities of the atomic world were to be conceived after the manner of bodies or mechanisms immensely small » (E. Persico, Fondamenti della meccanica atomica, Bologna 1945, p. 68, cf. p. 87). Consequently it affirms that the corpuscle, for example the electron, on entering higher complexes, loses its physical individuality, since it cannot be marked and followed, and remains as a modification of the complex. « The property of individuality does not in that case correspond to any physical reality » (ibid., p. 467; cf. P. Langevin, La notion de corpuscules et d'atomes, Paris 1935); L. De Broglie (Materia e luce, Milan 1940, p. 274) writes: « In quantum physics, the system is a kind of organism in whose unity the elementary constituent units are almost absorbed ». This concept is similar to that of the virtual existence of the components in the compound, developed by Aristotle and St. Thomas. One can therefore conclude that physical experiments do not seem to exclude hylomorphism, and in particular quantum mechanics develops concepts that are favorable to it.
By analogy with the concepts of hylomorphism, one often speaks of matter and form in disparate fields. E. Kant generally calls the manifold matter, while form is that by which the manifold is ordered (cf. Critica della ragion pura, Italian trans. by G. Gentile and G. Lombardo-Radice, Bari 1945, p. 64). There are « forms » of intuition, external (space), internal (time), of thought (categories), of pure reason (ideas), etc.
In sacramental theology the masters of the 12th and 13th centuries formulated the general doctrine according to which every Sacrament, insofar as it is a sensible sign, is composed of things (res) and of words (verba). Guided by analogy and observing that the res has an indeterminate meaning, while words have a precise sense, they called the former the « matter », the latter the « form » of the Sacrament.