Body

BODY. - In general, a body is a sensible material reality. In experimental science, a body is a portion of matter with determinate specific properties (dimensions, weight, density, chemical reactions, etc.). A distinction is drawn between simple bodies and compound bodies (v. composto). Philosophically, the body is a material substance, that is, a reality subsisting in itself, perceptible by means of the senses.

Speculation on the essence and the constitutive principles of bodies constitutes, as is well known, the principal object of the first Greek philosophy. The ancient Ionians posited as the foundation of material reality a common principle (ἀρχή, φύσις) from which bodies originate and to which they return, variously modified (cf. Aristotle, Phys., I, 4, 187 a 12 ff.). For Thales this principle is water, for Anaximander the infinite (ἄπειρον), for Anaximenes air (id., Met., I, 3, 983 b). The Pythagoreans, on the other hand, maintained that the principle of which bodies are made is number (ibid., I, 5, 983 b). According to Empedocles, compound bodies result from the mechanical composition of the elements (earth, water, air, fire), divided into particles and immutable (Prgm. 8, 9, 11); similarly Anaxagoras, who admitted infinite elements, indefinitely divisible (Prgm. 1, 4, 17). The atomists (Leucippus and Democritus) held that the primordial bodies are the atoms, essentially simple, indivisible, immutable, of different shapes; these, combining in various ways, give origin to all bodies (cf. Aristotle, Met., I, 4, 985 b 5 ff.; v. ATOMISMO). For Plato, bodies, various and mutable, are a participation in or imitation of the immutable subsisting ideas; bodies consist of space (χώρα), which remains unchanged in the changing of bodies, is like a "receptacle" (ὑποδοχή), a "nurse" (τιθήνη), a "matrix," receives within itself all forms (μορφή) without having one of its own (ἄμορφον ὄν: Tim., 48 e 52 d). These notions, obscure in Plato, are developed by Aristotle, for whom the body is essentially composite (σύνολον) of a substratum, called matter (ὕλη), and of a form (μορφή): γίγνεται πᾶν ἐκ τε τοῦ ὑποκειμένου καὶ τῆς μορφῆς (Phys., I, 7, 190 b 20).

Matter is the substratum of the mutations of bodies (ibid., I, 9, 192 a 31). It is in itself indeterminate: "I call matter that which in itself is not a determinate thing, nor quantity, nor any other of the determinations of being" (Met., VII, 3, 1029 a 20). Form is the determinate and determining element: it is not a complete entity, it is not generated in the proper sense (ibid., VIII, 3, 1043 b 15; 5, 1044 b 21-23, etc.). This doctrine of hylomorphism (v.) passed to the Greek, Arab and Latin Aristotelian school and was developed by St. Thomas, who clarified it in its consequences. It is, on the other hand, substantially modified by Scotus, who denies that prime matter is pure potency with respect to every act (Opus Oxon., II, d. 12, q. 1, 2, in Opera omnia, ed. L. Wadding, VI, Lyon 1639, p. 664 ff.), similarly by F. Suárez (Disputationes metaphysicae, d. 13, s. 5: in Opera omnia, ed. L. Vivès, XXV, Paris 1856-61, p. 414 ff.) and by their schools.

In modern philosophy the position of Descartes is well known, according to which the body is essentially extension: "Percipiemus naturam materiae sive corporis in universum spectati non consistere in eo quod sit res dura... sed tantum in eo quod sit res extensa in longum, latum et profundum" (Principia philosophiae, II, n. 4: in Opera omnia, ed. C. Adam and P. Tannery, VIII, Paris 1897-1910, p. 42); therefore it has only the dimensional properties of matter, divisibility, motion, figure, etc. For Spinoza, on the other hand, the body is a mode of the one, infinite Substance, considered insofar as it is extended: "Per corpus intelligo modum, qui Dei essentiam, quatenus ut res extensa consideratur, certo et determinato modo exprimit" (Ethica, ed. G. Gentile, Bari 1933, p. 47). Leibniz conceives the body as an aggregate of monads, simple, active substances; consequently its extension is phenomenal (cf. Letter to M. Arnauld, ed. Dutens, II, part 1, Geneva 1768, p. 46).

In the English school, noteworthy for its resolute immaterialism is the position of Berkeley, for whom the body is a complex of impressions caused in our spirit by God: "The ideas impressed on our spirit by the author of nature are called real things" (A Treatise Concerning the Principles of Human Knowledge, n. 33: Ital. trans. by G. Papini, Bari 1925, p. 40). "Their esse (of sensible things) is percipi, and it is not possible that they should have existence outside the minds or thinking things that perceive them" (ibid., n. 3, ed. cit., p. 26). For D. Hume the opinion of the continued, and therefore by us distinct, existence of bodies arises not from the senses but from the coherence and constancy of certain impressions which, always returning the same, we suppose "to be connected in a real existence, of which nevertheless we are not conscious" (A Treatise of Human Nature, I, part 4, sec. 2, n. 6: trans. by A. Carlini, Bari 1926, p. 245). In conclusion, Hume's skepticism "is constrained to admit the existence of bodies, although it cannot claim to sustain their reality by any philosophical argument" (ibid., n. 1: ed. cit., p. 231).

According to E. Kant, the body or nature is the thing as perceived by us through the a priori forms, not the thing in itself: "By nature is understood the existence of things insofar as they are determined by general laws. If 'nature' meant the existence of things in themselves, we could never know it, neither a priori nor a posteriori" (Prolegomena to Any Future Metaphysics, trans. by P. Martinetti, Bari 1924, p. 92). In Hegel bodies (nature) are the first externalization of the Idea from itself, its becoming other than itself, extending in space and time; only after this externalization does the Idea return into itself, knowing itself, and becomes thought of itself, that is, Spirit (Encyclopedia of the Philosophical Sciences in Outline, trans. by B. Croce, Bari 1923, p. 199). G. Gentile thinks that bodies are the spatial and temporal world, the world of the manifold, nature, which is outside the Spirit, but is the life of the Spirit: "Nature... is not intelligible except as the life of the Spirit, which indeed multiplies itself, but remains one" (General Theory of the Spirit, Florence 1938, p. 126). For materialism, on the other hand, the body is the only existing reality, from which everything derives; and for phenomenalism, a pure complex of sensitive and subjective representations.

In modern physics bodies are conceived as aggregates of extended particles, which are the fundamental constitutive elements of matter, bound to one another by forces; the recent theory of quantum mechanics, while accepting the particulate constitution of matter, thinks of the body as a complex of corpuscles-waves, which in the compound body lose their physical individuality (v. MATERIA). These scientific theories leave open the philosophical problem of the ontological unity of the compound body.

Roberto Masi