Plato, Laws 896a

ἄλλον πλὴν τὸν νυνδὴ ῥηθέντα, τὴν δυναμένην αὐτὴν αὑτὴν κινεῖν κίνησιν; τὸ ἑαυτὸ κινεῖν φῂς λόγον ἔχειν τὴν αὐτὴν οὐσίαν, ἥνπερ τοὔνομα ὃ δὴ πάντες ψυχὴν προσαγορεύομεν; φημί γε· εἰ δʼ ἔστι τοῦτο οὕτως ἔχον, ἆρα ἔτι ποθοῦμεν μὴ ἱκανῶς δεδεῖχθαι ψυχὴν ταὐτὸν ὂν καὶ τὴν πρώτην γένεσιν καὶ κίνησιν τῶν τε ὄντων καὶ γεγονότων καὶ ἐσομένων καὶ πάντων αὖ τῶν ἐναντίων τούτοις, ἐπειδή γε

Can we give it any other definition than that stated just now—the motion able to move itself? Do you assert that self-movement is the definition of that very same substance which has soul as the name we universally apply to it? That is what I assert. And if this be really so, do we still complain that it has not been sufficiently proved that soul is identical with the prime origin and motion of what is, has been, and shall be, and of all