Earlier in II.4 Aristotle has shown that the soul is the moving cause for nutrition.
ἐπεὶ δ’ ἡ αὐτὴ δύναμις τῆς ψυχῆς θρεπτικὴ καὶ γεννητική, περὶ τροφῆς ἀναγκαῖον διωρίσθαι πρῶτον· ἀφορίζεται γὰρ πρὸς τὰς ἄλλας δυνάμεις τῷ ἔργῳ τούτῳ. (416a19-21)
τροφῆς can refer to either food, nutrition, or the exercise of the faculty of nutrition.
ἔτι πάσχει τι ἡ τροφὴ ὑπὸ τοῦ τρεφομένου, ἀλλ’ οὐ τοῦτο ὑπὸ τῆς τροφῆς, ὥσπερ οὐδ’ ὁ τέκτων ὑπὸ τῆς ὕλης, ἀλλ’ ὑπ’ ἐκείνου αὕτη· ὁ δὲ τέκτων μεταβάλλει μόνον εἰς ἐνέργειαν ἐξ ἀργίας. (416a35-b3)
What undergoes change in the nutritive process, the food or that which is fed, i.e., the ensouled body (416b22)? Carpenter: wood = that which is fed: food
416a26-27 Fire: water = that which is fed: food
Water is food of fire, though fire does not feed water. Polansky (214) has an interpretation of how water feeds fire.
πότερον δ’ ἐστὶν ἡ τροφὴ τὸ τελευταῖον προσγινόμενον ἢ τὸ πρῶτον, ἔχει διαφοράν. εἰ δ’ ἄμφω, ἀλλ’ ἡ μὲν ἄπεπτος ἡ δὲ πεπεμμένη, ἀμφοτέρως ἂν ἐνδέχοιτο τὴν τροφὴν λέγειν· ᾗ μὲν γὰρ ἄπεπτος, τὸ ἐναντίον τῷ ἐναντίῳ τρέφεται, ᾗ δὲ πεπεμμένη, τὸ ὅμοιον τῷ ὁμοίῳ. ὥστε φανερὸν ὅτι λέγουσί τινα τρόπον ἀμφότεροι καὶ ὀρθῶς καὶ οὐκ ὀρθῶς. (416b3-9)
Two stages of food: (a) the undigested (τὸ πρῶτον, ἄπεπτος) and (b) the already digested (τὸ τελευταῖον, πεπεμμένη). Food before it is digested is actually unlike that which is fed, but potentially like it. In the course of digestion it becomes assimilated to the form of its mover.
ἐπεὶ δ’ οὐθὲν τρέφεται μὴ μετέχον ζωῆς, τὸ ἔμψυχον ἂν εἴη σῶμα τὸ τρεφόμενον, ᾗ ἔμψυχον, ὥστε καὶ ἡ τροφὴ πρὸς ἔμψυχόν ἐστι, καὶ οὐ κατὰ συμβεβηκός. (416b9-11)
"Perhaps we may say that the internal fire or heat of a living thing is fed incidentally (κατὰ συμβεβηκός) when the living thing feeds; the living ting itself is not thus fed only accidentally but in virtue of itself." (Polanksy, 216)
ἔστι δ’ ἕτερον τροφῇ καὶ αὐξητικῷ εἶναι· ᾗ μὲν γὰρ ποσόν τι τὸ ἔμψυχον, αὐξητικόν, ᾗ δὲ τόδε τι καὶ οὐσία, τροφή (σώζει γὰρ τὴν οὐσίαν, καὶ μέχρι τούτου ἔστιν ἕως ἂν τρέφηται), καὶ γενέσεως ποιητικόν, οὐ τοῦ τρεφομένου, ἀλλ’ οἷον τὸ τρεφόμενον· ἤδη γὰρ ἔστιν αὐτοῦ ἡ οὐσία, γεννᾷ δ’ οὐθὲν αὐτὸ ἑαυτό, ἀλλὰ σώζει. (11-17)
Growth pertains to the ensouled body insofar as it is quantitative, whereas nutrition in the narrow sense (τροφή) to the ensouled body insofar as it is an individual and substance (τόδε τι καὶ οὐσία), since the latter preserves the substance and keeps it exist or be what it is.
ὥσθ’ ἡ μὲν τοιαύτη τῆς ψυχῆς ἀρχὴ δύναμίς ἐστιν οἵα σώζειν τὸ ἔχον αὐτὴν ᾗ τοιοῦτον, ἡ δὲ τροφὴ παρασκευάζει ἐνεργεῖν· διὸ στερηθὲν τροφῆς οὐ δύναται εἶναι. (17-20)
[ἐπεὶ δ’ ἔστι τρία, τὸ τρεφόμενον καὶ ᾧ τρέφεται καὶ τὸ τρέφον, τὸ μὲν τρέφον ἐστὶν ἡ πρώτη ψυχή, τὸ δὲ τρεφόμενον τὸ ἔχον ταύτην σῶμα, ᾧ δὲ τρέφεται, ἡ τροφή.] (20-23)
ἐπεὶ δὲ ἀπὸ τοῦ τέλους ἅπαντα προσαγορεύειν δίκαιον, τέλος δὲ τὸ γεννῆσαι οἷον αὐτό, εἴη ἂν ἡ πρώτη ψυχὴ γεννητικὴ οἷον αὐτό. (23-25)
<ἐπεὶ δ’ ἔστι τρία, τὸ τρεφόμενον καὶ ᾧ τρέφεται καὶ τὸ τρέφον, τὸ μὲν τρέφον ἐστὶν ἡ πρώτη ψυχή, τὸ δὲ τρεφόμενον τὸ ἔχον ταύτην σῶμα, ᾧ δὲ τρέφεται, ἡ τροφή.> (25a-c)
ἔστι δὲ ᾧ τρέφει διττόν, ὥσπερ καὶ ᾧ κυβερνᾷ καὶ ἡ χεὶρ καὶ τὸ πηδάλιον, τὸ μὲν κινοῦν καὶ κινούμενον, τὸ δὲ κινούμενον μόνον. (25-27)
The easier reading
Soul: the ensouled body: food = the hand: ship: rudder
Food and the rudder: τὸ κινούμενον μόνον
Soul and the hand: τὸ κινοῦν καὶ κινούμενον
(Polansky, 220)
"Serving the role analogous to the hand in steering the ship is heat that he for present purposes leaves unclarified. Generation of Animals 736b29-737a7 denies that digestion could be due merely to fire and proposes instead pneuma as the hot material in the living things, whereas On Respiration 8.474a25-28 and b10-13 refers explicitly to fire in connection with digestion. Could mention of heat as comparable to the hand permit nutrition a sequence of instruments? Closest to the nutritive soul and able to work most subtly with it is pneuma. Pneuma has the fineness and adaptability of the human hand, and therefore is the soul's vital instrument (see GA 789b7-12)." (Polansky, 221)
πᾶσαν δ’ ἀναγκαῖον τροφὴν δύνασθαι πέττεσθαι, ἐργάζεται δὲ τὴν πέψιν τὸ θερμόν· διὸ πᾶν ἔμψυχον ἔχει θερμότητα. (28-29)
τύπῳ μὲν οὖν ἡ τροφὴ τί ἐστιν εἴρηται· διασαφητέον δ’ ἐστὶν ὕστερον περὶ αὐτῆς ἐν τοῖς οἰκείοις λόγοις. (30-31)
