[46] Aristot. De Animâ, I. i. p. 403, a. 25: τὰ πάθη λόγοι ἔνυλοί εἰσιν. Compare II. p. 412, b. 10-25; p. 413, a. 2.
[47] Ibid. I. i. p. 403, a. 30.
[48] Ibid. iv. p. 408, b. 12. τὸ δὲ λέγειν ὀργίζεσθαι τὴν ψυχὴν ὅμοιον κἂν εἴ τις λέγοι τὴν ψυχὴν ὑφαίνειν ἢ οἰκοδομεῖν· βέλτιον γὰρ ἴσως μὴ λέγειν τὴν ψυχὴν ἐλεεῖν ἢ μανθάνειν ἢ διανοεῖσθαι, ἀλλὰ τὸν ἄνθρωπον τῇ ψυχῇ· τοῦτο δὲ μὴ ὡς ἐν ἐκείνῃ τῆς κινήσεως οὔσης, ἀλλ’ ὅτε μὲν μέχρι ἐκείνης, ὅτε δ’ ἀπ’ ἐκείνης, &c. Again, b. 30: ὅτι μὲν οὖν οὐχ οἷόν τε κινεῖσθαι τὴν ψυχήν, φανερὸν ἐκ τούτων.
[49] Ibid. b. 26. Compare a similar doctrine in the Timæus of Plato, p. 86, B.-D.
Respecting the Noûs (the theorizing Noûs), we must here observe that Aristotle treats it as a separate kind or variety of soul, with several peculiarities. We shall collect presently all that he says upon that subject, which is the most obscure portion of his psychology.
In regard to soul generally, the relative point of view with body as the correlate is constantly insisted on by Aristotle; without such correlate his assertions would have no meaning. But the relation between them is presented in several different ways. The soul is the cause and principle of a living body;[50] by which is meant, not an independent and pre-existent something that brings the body into existence but, an immanent or indwelling influence which sustains the unity and guides the functions of the organism. According to the quadruple classification of Cause recognized by Aristotle — Formal, Material, Movent, and Final — the body furnishes the Material Cause, while the soul comprises all the three others. The soul is (as we have already seen) the Form in relation to the body as Matter, but it is, besides, the Movent, inasmuch as it determines the local displacement as well as all the active functions of the body — nutrition, growth, generation, sensation, &c.; lastly, it is also the Final Cause, since the maintenance and perpetuation of the same Form, in successive individuals, is the standing purpose aimed at by each body in the economy of Nature.[51] Under this diversity of aspect, soul and body are reciprocally integrant and complementary of each other, the real integer (the Living or Animated Body) including both.
[50] Aristot. De Animâ, II. iv. p. 415, b. 7: ἔστι δ’ ἡ ψυχὴ τοῦ ζῶντος σώματος αἰτία καὶ ἀρχή· ταῦτα δὲ πολλαχῶς λέγεται.
[51] Ibid. b. 1.
Soul, in the Aristotelian point of view — what is common to all living bodies, comprises several varieties. But these varieties are not represented as forming a genus with co-ordinate species under it, in such manner that the counter-ordinate species, reciprocally excluding each other, are, when taken together, co-extensive with the whole genus; like man and brute in regard to animal. The varieties of soul are distributed into successive stages gradually narrowing in extension and enlarging in comprehension; the first or lowest stage being co-extensive with the whole, but connoting only two or three simple attributes; the second, or next above, connoting all these and more besides, but denoting only part of the individuals denoted by the first; the third connoting all this and more, but denoting yet fewer individuals; and so on forward. Thus the concrete individuals, called living bodies, include all plants as well as all animals; but the soul, called Nutritive by Aristotle, corresponding thereto connotes only nutrition, growth, decay, and generation of another similar individual.[52] In the second stage, plants are left out, but all animals remain: the Sentient soul, belonging to animals, but not belonging to any plants, connotes all the functions and unities of the Nutritive soul, together with sensible perception (at least in its rudest shape) besides.[53] We proceed onward in the same direction, taking in additional faculties — the Movent, Appetitive, Phantastic (Imaginative), Noëtic (Intelligent) soul, and thus diminishing the total of individuals denoted. But each higher variety of soul continues to possess all the faculties of the lower. Thus the Sentient soul cannot exist without comprehending all the faculties of the Nutritive, though the Nutritive exists (in plants) without any admixture of the Sentient. Again, the Sentient soul does not necessarily possess either memory, imagination, or intellect (Noûs); but no soul can be either Imaginative or Noëtic, without being Sentient as well as Nutritive. The Noëtic Soul, as the highest of all, retains in itself all the lower faculties; but these are found to exist apart from it.[54]
[52] In the Aristotelian treatise De Plantis, p. 815, b. 16, it is stated that Empedokles, Anaxagoras, and Demokritus, all affirmed that plants had both intellect and cognition up to a certain moderate point. We do not cite this treatise as the composition of Aristotle, but it is reasonably good evidence in reference to the doctrine of those other philosophers.