LCL 288: 412-413
ΠΕΡΙ ΝΕΟΤΗΤΟΣ ΚΑΙ ΓΗΡΩΣ ΠΕΡΙ ΖΩΗΣ ΚΑΙ ΘΑΝΑΤΟΥ
10I. Περὶ δὲ νεότητος καὶ γήρως καὶ περὶ ζωῆς καὶ θανάτου λεκτέον νῦν· ἅμα δὲ καὶ περὶ ἀναπνοῆς ἀναγκαῖον ἴσως τὰς αἰτίας εἰπεῖν· ἐνίοις γὰρ τῶν ζῴων διὰ τοῦτο συμβαίνει τὸ ζῆν καὶ τὸ μὴ ζῆν. ἐπεὶ δὲ περὶ ψυχῆς ἐν ἑτέροις διώρισται, καὶ δῆλον ὅτι οὐχ οἷόν τ᾿ εἶναι σῶμα τὴν οὐσίαν αὐτῆς, ἀλλ᾿ 15ὅμως ὅτι γ᾿ ἔν τινι τοῦ σώματος ὑπάρχει μορίῳ, φανερόν, καὶ ἐν τούτῳ τινὶ τῶν ἐχόντων δύναμιν ἐν τοῖς μορίοις. τὰ μὲν οὖν ἄλλα τῆς ψυχῆς ἢ μόρια ἢ δυνάμεις, ὁποτέρως ποτὲ δεῖ καλεῖν, ἀφείσθω τὰ νῦν· ὅσα δὲ ζῷα λέγεται καὶ ζῆν, ἐν μὲν τοῖς 20ἀμφοτέρων τούτων τετυχηκόσι (λέγω δ᾿ ἀμφοτέρων τοῦ τε ζῷον εἶναι καὶ τοῦ ζῆν) ἀνάγκη ταὐτὸν εἶναι καὶ ἓν μόριον καθ᾿ ὅ τε ζῇ καὶ καθ᾿ ὃ προσαγορεύομεν αὐτὸ ζῷον. τὸ μὲν γὰρ ζῷον ᾗ ζῷον, ἀδύνατον μὴ ζῆν· ᾗ δὲ ζῇ, ταύτῃ ζῷον ὑπάρχειν οὐκ ἀναγκαῖον· τὰ γὰρ φυτὰ ζῇ μέν, οὐκ ἔχει δ᾿ 25αἴσθησιν, τῷ δ᾿ αἰσθάνεσθαι τὸ ζῷον πρὸς τὸ μὴ ζῷον διορίζομεν.
Ἀριθμῷ μὲν οὖν ἀναγκαῖον ἓν εἶναι καὶ τὸ αὐτὸ τοῦτο τὸ μόριον, τῷ δ᾿ εἶναι πλείω καὶ ἕτερα· οὐ
On Youth and Old Age on Life and Death
I. We must now discuss youth and old age, lifeThe essential to life is sensation. and death. At the same time we shall presumably have also to describe the causes of respiration; for in some animals this constitutes the difference between living and not living. In another treatise we have given a detailed account of the soul, and while it is clear that its essence cannot be corporeal, yet it is equally clear that it resides in some part of the body which is among those which have control over the rest. We may now neglect the other parts or functions of the soul, whichever we should call them; but as for what we call animals and living, in anything to which both terms (vis., animal and living) are applicable, there must be one identical part in virtue of which the creature lives and we call it an animal. For the animal, in so far as it is such, cannot fail to live, but it need not be an animal because it lives; for plants live, but have no sensation, and it is by sensation that we distinguish the animal from that which is not animal.
Numerically, then, this part must be one and the same, but in essence more than one and differentiated;