In this paper, I ask for a picture of real Life of Christians in the multicultural world of the imperium Romanum during the first two centuries CE. Christians Lived in a mostly hostile society but interpreted their situation as a challenge for their Lives. I start with three short preliminary remarks, arguing first on New Testaments texts where the differences between "Christians" and non-Christians are marked sharply (e.g. the gospel of John or Romans 12:1-2), second on the characteristic religious pluralism in the Roman empire in the first and second centuries, third on the "absoluteness" claimed by Christians and Jews. In part two, I give a short survey on the self interpretation of the first community in Jerusalem and then of Pauline Christianity, taken primarily from the Pauline Letters and the Acts of Luke, at Last from the Letter to Diognetus. Christianity rapidly became a phenomenon of "globalization", because there is no "Christian nation" and no "Christian country" and no distinctive "Christian society". But Christian communities were distinguishable from others, recognized as a matter of its own. Who wants to persuade others, cannot keep them in distance but must approach them and at the same time has to be recognizable from outside. This in a conclusion is illustrated by 1 Corinthians ch. 14 where Paul shows that Christian preaching shall be understood by others.