**NATURE. -** It is the intrinsic principle of the becoming of corporeal beings, especially according to Aristotle, who derives the term φύσις from φύειν, which means to be born, to sprout, to grow (*Phys.*, II, 1, 193 b 16). Becoming (v.) is especially characteristic of living beings, of simple bodies which are called in the strict sense «natural bodies» as opposed to things produced by art, by chance (*ταυτόματον*) and by violence (*βία*): here phenomena occur without law or purpose because they are provoked externally, whereas in nature becoming actualizes the subject in conformity with the law of its being. For this reason Aristotle defines nature as «the first intrinsic principle of motion and rest» (*ibid.*, 192 b 20-22).
In the notion of nature Aristotle seeks to reconcile and transcend the opposition between the conception of the pre-Socratics, who did not admit anything beyond the materiality of beings, and the Platonic conception, which posited the laws of beings in the Ideas and the principle of the motion of bodies in the soul. Therefore he declares that nature applies to matter, but not to indeterminate and empty matter, rather to «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 in the proper sense nature is the form and the type (*μορφή καί είδος*) of beings that have within themselves the principle of change, the form which is not separable (from matter) except conceptually (*κατά λόγον*: *ibid.*, 193 b 2). In its immediate phenomenological sense nature was birth, as Empedocles (v.) said, opposed to death (fr. B, 8: Diels-Kranz, *Die Fragmente der Vorsokr.*, 5th ed., I, Berlin 1937, p. 312); but Aristotle, who elsewhere cites the text of Empedocles (*Met.*, V, 4, 1015 a ff.), fixed its metaphysical meaning within the scope of becoming (against Plato) but beyond mere phenomena (against the conception of the Sophists). Thus nature is the essence (*οὐσία*) understood as the whole that exists and operates (*δῆμα καί ἔπασα οὔσα*: *De Coelo I*, 2, 268 b 11). St. Thomas completes this latter derived meaning, which in ordinary usage is the principal one, with a reference to Boethius, who condensed 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). Taken in this strict sense, the concept of nature enters Catholic theology to determine the relations in God between the three Divine Persons and the single identical divine nature, and in Jesus Christ between the Person of the Word who subsists in two natures, the divine and the human assumed in the Incarnation: the clear distinction of the two natures entails the distinction of their respective operations and thus constitutes the foundation of merit and therefore of our redemption (*ibid.*, q. 9, aa. 1-4).
St. Thomas also distinguishes a universal nature (which can be God or some other principle that moves the becoming of beings), which some call *natura naturans*, and a particular nature (cf. Averroës, *In De coelo I*, 2, who has *natura naturata*): terminology that would become influential with Spinoza (*Ethica*, part 1, prop. XXIX, *scholion*).
**