Laudator Temporis Acti

Plato, Menexenus 17 (245 C-D; tr. R.G. Bury):

So firmly-rooted and so sound is the noble and liberal character of our city, and endowed also with such a hatred of the barbarian, because we are pure-blooded Greeks, unadulterated by barbarian stock. For there cohabit with us none of the type of Pelops, or Cadmus, or Aegyptus or Danaus, and numerous others of the kind, who are naturally barbarians though nominally Greeks; but our people are pure Greeks and not a barbarian blend; whence it comes that our city is imbued with a whole-hearted hatred of alien races.

οὕτω δή τοι τό γε τῆς πόλεως γενναῖον καὶ ἐλεύθερον βέβαιόν τε καὶ ὑγιές ἐστι καὶ φύσει μισοβάρβαρον, διὰ τὸ εἰλικρινῶς εἶναι Ἕλληνες καὶ ἀμιγεῖς βαρβάρων. οὐ γὰρ Πέλοπες οὐδὲ Κάδμοι οὐδὲ Αἴγυπτοί τε καὶ Δαναοὶ οὐδὲ ἄλλοι πολλοὶ φύσει μὲν βάρβαροι ὄντες, νόμῳ δὲ Ἕλληνες, συνοικοῦσιν ἡμῖν, ἀλλ᾿ αὐτοὶ Ἕλληνες, οὐ μιξοβάρβαροι οἰκοῦμεν, ὅθεν καθαρὸν τὸ μῖσος ἐντέτηκε τῇ πόλει τῆς ἀλλοτρίας φύσεως.