Plato, Laws 626d

αὐτῷ δὲ πρὸς αὑτὸν πότερον ὡς πολεμίῳ πρὸς πολέμιον διανοητέον; ἢ πῶς ἔτι λέγομεν; ὦ ξένε Ἀθηναῖε—οὐ γάρ σε Ἀττικὸν ἐθέλοιμʼ ἂν προσαγορεύειν· δοκεῖς γάρ μοι τῆς θεοῦ ἐπωνυμίας ἄξιος εἶναι μᾶλλον ἐπονομάζεσθαι· τὸν γὰρ λόγον ἐπʼ ἀρχὴν ὀρθῶς ἀναγαγὼν σαφέστερον ἐποίησας, ὥστε ῥᾷον ἀνευρήσεις ὅτι νυνδὴ ὑφʼ ἡμῶν ὀρθῶς ἐρρήθη τὸ πολεμίους εἶναι πάντας πᾶσιν δημοσίᾳ τε, καὶ ἰδίᾳ ἑκάστους αὐτοὺς σφίσιν αὐτοῖς.

And must each individual man regard himself as his own enemy? Or what do we say when we come to this point? O Stranger of Athens, for I should be loth to call you a man of Attica, since methinks you deserve rather to be named after the goddess Athena, seeing that you have made the argument more clear by taking it back again to its starting-point; whereby you will the more easily discover the justice of our recent statement that, in the mass, all men are both publicly and privately the enemies of all, and individually also each man is his own enemy.