449 b δ᾿ ἄνευ τῶν ἐνεργειῶν ἔχῃ τὴν ἐπιστήμην καὶ 20τὴν αἴσθησιν, οὕτω μέμνηται [τὰς τοῦ τριγώνου ὅτι δύο ὀρθαῖς ἴσαι],1 τὸ μὲν ὅτι ἔμαθεν ἢ ἐθεώρησεν, τὸ δὲ ὅτι ἤκουσεν ἢ εἶδεν ἢ ὅ τι τοιοῦτον· ἀεὶ γὰρ ὅταν ἐνεργῇ κατὰ τὸ μνημονεύειν, οὕτως ἐν τῇ ψυχῇ λέγει ὅτι πρότερον τοῦτο ἤκουσεν ἢ ᾔσθετο ἢ ἐνόησεν.
Ἔστι μὲν οὖν ἡ μνήμη οὔτε αἴσθησις οὔτε 25ὑπόληψις, ἀλλὰ τούτων τινὸς ἕξις ἢ πάθος, ὅταν γένηται χρόνος. τοῦ δὲ νῦν ἐν τῷ νῦν οὐκ ἔστι μνήμη, καθάπερ εἴρηται καὶ πρότερον, ἀλλὰ τοῦ μὲν παρόντος αἴσθησις, τοῦ δὲ μέλλοντος ἐλπίς, τοῦ δὲ γενομένου μνήμη. διὸ μετὰ χρόνου πᾶσα μνήμη. ὥσθ᾿ ὅσα χρόνου αἰσθάνεται, ταῦτα μόνα 30τῶν ζῴων μνημονεύει, καὶ τούτῳ ᾧ αἰσθάνεται.
Ἐπεὶ δὲ περὶ φαντασίας εἴρηται πρότερον ἐν τοῖς περὶ ψυχῆς, καὶ νοεῖν οὐκ ἔστιν ἄνευ φαντάσματος· 450 aσυμβαίνει γὰρ τὸ αὐτὸ πάθος ἐν τῷ νοεῖν ὅπερ καὶ ἐν τῷ διαγράφειν· ἐκεῖ τε γὰρ οὐθὲν προσχρώμενοι τῷ τὸ ποσὸν ὡρισμένον εἶναι τὸ τριγώνου, ὅμως γράφομεν ὡρισμένον κατὰ τὸ ποσόν· καὶ ὁ νοῶν ὡσαύτως, κἂν μὴ ποσὸν νοῇ, τίθεται πρὸ ὀμμάτων ποσόν, νοεῖ δ᾿ οὐχ ᾗ ποσόν. 5ἂν δ᾿ ἡ φύσις ᾖ τῶν ποσῶν, ἀόριστον δέ, τίθεται μὲν ποσὸν ὡρισμένον, νοεῖ δ᾿ ᾗ ποσὸν μόνον. διὰ τίνα μὲν οὖν αἰτίαν οὐκ ἐνδέχεται νοεῖν οὐδὲν ἄνευ τοῦ συνεχοῦς, οὐδ᾿ ἄνευ χρόνου τὰ μὴ ἐν χρόνῳ
has knowledge or sensation without the actualization of these faculties, then one remembers: in the former case that he learned or thought out the fact, and in the latter that he heard or saw it or perceived it in some other such way; for when a man is exercising his memory he always says in his mind that he has heard, or felt, or thought this before.
Memory, then, is neither sensation nor judgement,What is memory? but is a state or affection of one of these, when time has elapsed. There can be no memory of something now present at the present time, as has been said, but sensation refers to what is present, expectation to what is future, and memory to what is past. All memory, then, implies lapse of time. Hence only those living creatures which are conscious of time can be said to remember, and they do so with that part which is conscious of time.
We have already dealt with imagination in theThe part played by imagination. treatise On the Soul.a It is impossible even to think without a mental picture. The same affection is involved in thinking as in drawing a diagram; for in this case although we make no use of the fact that the magnitude of a triangle is a finite quantity, yet we draw it as having a finite magnitude. In the same way the man who is thinking, though he may not be thinking of a finite magnitude, still puts a finite magnitude before his eyes, though he does not think of it as such. And even if the nature of the object is quantitative, but indeterminate, he still puts before him a finite magnitude, although he thinks of it as merely quantitative. Why it is impossible to think of anything without continuity, or to think of things which are timeless except in terms of time, is another