Epicurus, Letter to Herodotus [=Diogenes Laertius 10.65]
“For this reason, because the soul is embodied, it never loses perception even if some part of it is removed. So, even if parts of the soul perish along with the container when it is destroyed completely or partially, should the soul in fact persist it retains perception. But the rest of the body that remains either whole or in parts does not have perception when this thing has been removed, that number of atoms requisite for the nature of the soul.
So, really, when the whole mass is destroyed, the soul scatters and no longer has the same abilities and can no longer move, just as if it never even obtained perception.”
“Διὸ δὴ καὶ ἐνυπάρχουσα ἡ ψυχὴ οὐδέποτε ἄλλου τινὸς μέρους ἀπηλλαγμένου ἀναισθητεῖ· ἀλλ᾿ ἃ ἂν καὶ ταύτης ξυναπόληται τοῦ στεγάζοντος λυθέντος εἴθ᾿ ὅλου εἴτε καὶ μέρους τινός, ἐάν περ διαμένῃ, ἕξει τὴν αἴσθησιν. τὸ δὲ λοιπὸν ἄθροισμα διαμένον καὶ ὅλον καὶ κατὰ μέρος οὐκ ἔχει τὴν αἴσθησιν κείνου ἀπηλλαγμένου, ὅσον ποτέ ἐστι τὸ συντεῖνον τῶν ἀτόμων πλῆθος εἰς τὴν τῆς ψυχῆς φύσιν. καὶ μὴν καὶ λυομένου τοῦ ὅλου ἀθροίσματος ἡ ψυχὴ διασπείρεται καὶ οὐκέτι ἔχει τὰς αὐτὰς δυνάμεις οὐδὲ κινεῖται, ὥσπερ οὐδ᾿ αἴσθησιν κέκτηται.