Originating in the circumstance of a multicultural church (primarily Jewish and Hellenistic), Ephesians addresses issues appropriate to the diverse religious and cultural backgrounds present in the community. Paul addresses hostility, division, and self-interest more than any other topic in the letter, leading many scholars to believe that his primary concern was not doctrinal, but behavioral. Some theologians agree the main theme of Ephesians is in response to the newly converted Jews who often separated themselves from their Gentile brethren. The unity of the church, especially between Jew and Gentile believers, is the keynote of the book. (Summary from Wikipedia)