Plato, Laws 899c

οὐκ ἔστιν οὕτως, ὦ ξένε, παραφρονῶν οὐδείς. τῷ μὲν τοίνυν μὴ νομίζοντι θεοὺς ἐν τῷ πρόσθεν χρόνῳ, ὦ Μέγιλλέ τε καὶ Κλεινία, εἰπόντες ὅρους ἀπαλλαττώμεθα. τίνας; ἢ διδάσκειν ἡμᾶς ὡς οὐκ ὀρθῶς λέγομεν τιθέμενοι ψυχὴν γένεσιν ἁπάντων εἶναι πρώτην, καὶ τἆλλα ὁπόσα τούτων συνεπόμενα εἴπομεν, ἢ μὴ δυνάμενον βέλτιον λέγειν ἡμῶν, ἡμῖν πείθεσθαι καὶ ζῆν θεοὺς ἡγούμενον εἰς τὸν ἐπίλοιπον

There is not a man, Stranger, so wrong-headed as that. Let us, then, lay down limiting conditions for the man who up till now disbelieves in gods, O Megillus and Clinias, and so be quit of him. What conditions? That either he must teach us that we are wrong in laying down that soul is of all things the first production, together with all the consequential statements we made,—or, if he is unable to improve on our account, he must believe us, and for the rest of his life live in veneration of the gods.