Since the beginning, Christians have lived in, and been a part of, political, cultural and economic communities which largely do not share their morality or faith. This creates tensions which are addressed in the Gospels and in the earliest examples of Christian apologetics, such as the Letter to Diognetus (from which the title of this essay is drawn). One aspect of this tension is the relationship of “Church and State,” but another is the situation faced by individual Christians or Christian families in the world.
These tensions are psychological, but not only that. We naturally want to be in harmony with those around us so strong differences in values on important matters create an inner tension. Much of casual conversation, such as that which may take place in the check-out line at the grocery store, is based on presumed shared cultural values. Since society's morality is reflected in law, in extreme circumstances, Christians can find themselves economically penalized for living their faith or even excluded from aspects of public life and culture.
Some efforts to address this tension are more adequate than others, with attempts to “resolve” the tension completely being among the most inadequate. One such resolution is for Christians to refuse to be part of the political, cultural and economic community – a kind of secession or conscientious objection to any cooperation with non-Christian communities. This may include a utopian impulse to found “Christian cities” or communities where Christians can shop at Christian stores and only see Christian movies and read only Christian newspapers. In its worst instances, this is coupled with a disinterest or even contempt for the fate and situation of those “outside” the community.
The opposite impulse is to resolve the tension by simply adopting the same values and lifestyles as the dominant communities. In politics you vote like other persons of your educational and economic class. In culture you share the “sophisticated” views of the contemporary cultural leaders of your society. And in economics you are the quintessential American consumer. You go to Church on Sunday, but by conforming your faith to the dominant situation, any tension is avoided.
In contrast to these opposing errors, here is how the Letter to Diognetus describes the adventure of the lived tension of the Christian life in 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. .... 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.