Here are some excerpts from the patristic reading designated in the Liturgy of the Hours -- Office of Readings for today (May 13, 2020).
The Epistle of Mathetes to Diognetus (A.D. 130) points to Christians -- the Body of Christ, the Church, as the persecuted witness to truth in the world but not of the world.
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. Their teaching is not based upon reveries inspired by the curiosity of men. Unlike some other people, they champion no purely human doctrine.
. . . . 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 labour 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 . . . . 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. They are defamed, but vindicated. A blessing is their answer to abuse, deference their response to insult. For the good they do they receive the punishment of malefactors, but even then they rejoice, as though receiving the gift of life. They are attacked by the Jews as aliens, they are persecuted by the Greeks, yet no one can explain the reason for this hatred.
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 world hates the Christians, not because they have done it any wrong, but because they are opposed to its enjoyments.
Christians love those who hate them just as the soul loves the body and all its members
. . . . It is by the soul, enclosed within the body, that the body is held together, and similarly, it is by the Christians, detained in the world as in a prison, that the world is held together.
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 . . . .