Plato, Laws 887a

ὡς δεινὰ ἐργαζόμεθα νομοθετοῦντες ὡς ὄντων θεῶν; ἢ χαίρειν ἐάσαντες ἐπὶ τοὺς νόμους τρεπώμεθα πάλιν, μὴ καὶ τὸ προοίμιον ἡμῖν μακρότερον γίγνηται τῶν νόμων; οὐ γάρ τι βραχὺς ὁ λόγος ἐκταθεὶς ἂν γίγνοιτο, εἰ τοῖσιν ἐπιθυμοῦσιν ἀσεβεῖν τὰ μὲν ἀποδείξαιμεν μετρίως τοῖς λόγοις ὧν ἔφραζον δεῖν πέρι λέγειν, τὸν δὲ εἰς φόβον τρέψαιμεν, τὰ δὲ δυσχεραίνειν ποιήσαντες, ὅσα πρέπει μετὰ ταῦτα ἤδη νομοθετοῖμεν.

of doing something dreadful by assuming in our legislation the existence of gods? Or shall we rather dismiss the whole subject and revert again to our laws, lest our prelude prove actually more lengthy than the laws? For indeed our discourse would be extended in no small degree if we were to furnish those men who desire to be impious with an adequate demonstration by means of argument concerning those subjects which ought, as they claimed, to be discussed, and so to convert them to fear of the gods, and then finally, when we had caused them to shrink from irreligion, to proceed to enact the appropriate laws.