The Way of the Fathers (which should run in every church bulletin) calls attention to the Letter to Diognetus, a Second Century work of Christian apologetics. You can read the whole thing in twenty minutes, but let me call attention to this passage, excerpted on the Vatican website, which offers some insight into how Second Century Christians answered the sorts of questions discussed in the comments on this post below:
Christians are indistinguishable from other men either by nationality, language or customs. They do not inhabit separate cities of their own, or speak a strange dialect, or follow some outlandish way of life... With regard to dress, food and manner of life in general, they follow the customs of whatever city they happen to be living in, whether it is Greek or foreign.
And yet there is something extraordinary about their lives. They live in their own countries as though they were only passing through. They play their full role as citizens, but labor under all the disabilities of aliens. Any country can be their homeland, but for them their homeland, wherever it may be, is a foreign country. Like others, they marry and have children, but they do not expose them. They share their meals, but not their wives.
They live in the flesh, but they are not governed by the desires of the flesh. They pass their days upon earth, but they are citizens of heaven. Obedient to the laws, they yet live on a level that transcends the law. Christians love all men, but all men persecute them. Condemned because they are not understood, they are put to death, but raised to life again. They live in poverty, but enrich many; they are totally destitute, but possess an abundance of everything. They suffer dishonor, but that is their glory....
To speak in general terms, we may say that the Christian is to the world what the soul is to the body. As the soul is present in every part of the body, while remaining distinct from it, so Christians are found in all the cities of the world, but cannot be identified with the world. As the visible body contains the invisible soul, so Christians are seen living in the world, but their religious life remains unseen. The body hates the soul and wars against it, not because of any injury the soul has done it, but because of the restriction the soul places on its pleasures. Similarly, the world hates the Christians, not because they have done it any wrong, but because they are opposed to its enjoyments.
.... The soul, though immortal, has a mortal dwelling place; and Christians also live for a time amidst perishable things, while awaiting the freedom from change and decay that will be theirs in heaven. As the soul benefits from the deprivation of food and drink, so Christians flourish under persecution. Such is the Christian's lofty and divinely appointed function, from which he is not permitted to excuse himself.