NATURA. – It is the intrinsic principle of the becoming of corporeal beings, especially according to Aristotle, who derives the term φύσις from φύσιναι, which means to be born, sprout, and grow (Phys., II, 1, 193 b 16). Becoming (v.) belongs above all to living things and to the simple bodies that are called, strictly speaking, “natural bodies”; opposed to these are things produced by art, chance (ταὐτόματον), and violence (βία): in the latter, phenomena occur without law or purpose because they are brought about from outside, whereas in n. becoming actualizes the subject in conformity with the law of its being. Aristotle therefore defines n. as “the first intrinsic principle, in itself, of motion and rest” (ibid., 192 b 20-22).
In the notion of n., Aristotle seeks to reconcile and overcome the opposition between the conception of the Presocratics, who admitted only the materiality of beings, and the Platonic conception, which placed the laws of beings in the Ideas and the principle of the movement of bodies in the soul. He therefore declares that n. applies to matter, though not to indeterminate and empty matter, but to that “immediate [matter] which serves as the subject of each of the beings that have within themselves the principle of motion and change” (ibid., 193 a 28). Yet, properly speaking, n. is “the form and type (μορφὴ καὶ εἶδος) of beings that have within themselves the principle of change,” the form that is separable (from matter) only conceptually (κατὰ λόγον; ibid., 193 b 2). In its immediate phenomenological sense, n. was birth, as Empedocles (v.) said, opposed to death (fr. B, 8: Diels-Kranz, Die Fragmente der Vorsokr., 5ª ed., I, Berlin 1937, p. 312); but Aristotle, who elsewhere cites Empedocles’ text (Met., V, 4, 1015 a ff.), established its metaphysical meaning within the sphere of becoming (against Plato), but beyond mere phenomena (against the conception of the Sophists). Thus n. is essence (οὐσία), understood as the whole that exists and acts (ὅλη καὶ ἄπασα οὐσία: De Coelo I, 2, 268 b 11). S. Tommaso completes this latter derived meaning, which in ordinary usage is the principal one, by referring to Boethius, who gathered the Aristotelian physical-metaphysical process into a logical-metaphysical definition: “Natura est unamquamque rem informans specifica differentia” (De duabus naturis, cap. 1: PL 64, 1342; cf. Sum. Theol., 3ª, q. 2, a. 1). Understood with this rigor, the concept of n. enters Catholic theology in order to determine the relations in God between the three Divine Persons and the one identical divine n., and in Jesus Christ between the Person of the Word, who subsists in two n., the divine and the human assumed through the Incarnation: the clear distinction between the two n. entails the distinction between their respective operations and therefore constitutes the foundation of merit and consequently of our redemption (ibid., q. 9, aa. 1-4).
S. Tommaso also distinguishes a universal n. (which may be God or some other principle that moves the becoming of beings), which some call n. naturans, and a particular n. (cf. Averroé, In De coelo, I, 2, which has n. naturata): terminology that would enjoy success with Spinoza (Ethica, parte 1ª, prop. XXIX, scholion).