Plato, Laws 777b

τί οὖν δὴ χρὴ ποιεῖν, τούτων, ὦ ξένε, διαφερομένων οὕτω, περὶ τῆς ἡμετέρας αὖ χώρας ἡμᾶς, τῆς τε κτήσεως ἅμα καὶ κολάσεως τῶν δούλων πέρι; τί δʼ, ὦ Κλεινία; δῆλον ὡς ἐπειδὴ δύσκολόν ἐστι τὸ θρέμμα ἄνθρωπος, καὶ πρὸς τὴν ἀναγκαίαν διόρισιν, τὸ δοῦλόν τε ἔργῳ διορίζεσθαι καὶ ἐλεύθερον καὶ δεσπότην, οὐδαμῶς εὔχρηστον ἐθέλειν εἶναί τε καὶ γίγνεσθαι φαίνεται,

Since this difference of opinion exists, Stranger, what ought we to do about our own country, in regard to the owning of slaves and their punishment? Well now, Clinias, since man is an intractable creature, it is plain that he is not at all likely to be or become easy to deal with in respect of the necessary distinction between slave and free-born master in actual experience. That is evident. The slave is no easy chattel. For actual experience shows