[This is another excerpt from the Epistle to Diognetus, written circa 129 AD, translated by J.B. Lightfoot, © 1936.]
In a word, what the soul is in a body, this the Christians are in the world. The soul is spread through all the members of the body, and Christians through the divers cities of the world. The soul hath its abode in the body, and yet it is not of the body. So Christians have their abode in the world, and yet they are not of the world.
The soul which is invisible is guarded in the body which is visible: so Christians are recognised as being in the world, and yet their religion remaineth invisible. The flesh hateth the soul and wageth war with it, though it receiveth no wrong, because it is forbidden to indulge in pleasures; so the world hateth Christians, though it receiveth no wrong from them, because they set themselves against its pleasures. The soul loveth the flesh which hateth it, and the members; so Christians love those that hate them.
The soul is enclosed in the body, and yet itself holdeth the body together; so Christians are kept in the world as in a prison-house, and yet they themselves hold the world together. The soul though itself immortal dwelleth in a mortal tabernacle; so Christians sojourn amidst perishable things, while they look for the imperishability which is in the heavens.
The soul when hardly treated in the matter of meals and drinks is improved; and so Christians when punished increase more and more daily. So great is the office for which God hath appointed them, and which it is not lawful for them to decline.