Christians are not distinguished from the rest of mankind by either country, speech or customs; the fact is, they nowhere settle in cities of their own; they use no peculiar language; they cultivate no eccentric mode of life. Certainly, this creed of theirs is no discovery due to some fancy or speculation of inquisitive men; nor do they, as some do, champion a doctrine of human origin…. They reside in their respective countries, but only as aliens. They take part in everything as citizens and put up with everything as foreigners. Every foreign land is their home, and every home a foreign land. They marry like all others and beget children; but they do not expose their offspring. Their board they spread for all, but not their bed. They find themselves in the flesh, but do not live according to the flesh. They spend their days on earth, but hold citizenship in heaven. They obey the established laws, but in their private lives they rise above the laws. They love all men, but are persecuted by all.
The Epistle to Diognetus (late 2nd Century) is one of the earliest examples of Christian apologetics and although sometimes attributed to “Mathetes” — which merely means “disciple” — most scholars generally agree on the anonymity of the author. About Diognetus, scholars agree less — some consider him to be a tutor of the Roman emperor Marcus Aurelius; others identify him as Claudius Diogenes, procurator of Alexandria in the late 2nd and early 3rd centuries.