Plato, Laws 861d

τοῦτο ὡς ὀρθῶς εἴρηται πρῶτον διορίσαντας δηλῶσαι. τούτοιν τοίνυν τοῖν δυοῖν τὸ μὲν οὐκ ἀνεκτὸν ἐμοὶ πάντως που γίγνεσθαι, τό γε δὴ μὴ λέγειν, οὕτως οἰόμενον ἔχειν τἀληθές—οὐ γὰρ ἂν νόμιμον οὐδʼ ὅσιον ἂν εἴη—κατὰ τίνα δὲ τρόπον ἐστὸν δύο, εἰ μὴ τῷ τε ἀκουσίῳ καὶ τῷ ἑκουσίῳ διαφέρετον ἑκάτερον; ἀλλὰ ἄλλῳ τινὶ δή ποτε πειρατέον ἁμῶς γέ πως δηλοῦν. παντάπασι μὲν οὖν, ὦ ξένε, τοῦτό γε οὐχ οἷόν τε ἄλλως πως ἡμᾶς διανοηθῆναι.

then prove the correctness of that assertion. Of these alternatives the first is to me quite intolerable—namely, not to assert what I hold to be the truth,—for that would be neither a lawful thing to do nor a pious. But as to the question how such acts are two-fold,—if the difference does not lie in that between the voluntary and the involuntary, then we must try to explain it by means of some other distinction. Well, certainly, Stranger, about this matter there is no other plan we can possibly adopt.