8.How many Lords are there?

One.

Every Christian in Heaven and on the earth worships the same Lord, Christ.

Paul is building up to his teaching concerning the perfecting of the one Body of Christ (verses 8-16). Christ, Head and Body, will consist of perfect members. If one member has not been brought to perfection the Body then is imperfect. The "one new man" of Chapter Two includes all of the members of the Body of Christ whether Jewish or Gentile by race.

In calling our attention to the oneness of the elements of Christianity, Paul is systematically cutting away any possible basis for the existence of a special denomination of Christians, of a special grouping of God’s people. It is not possible in Christ to distinguish between Jew and Gentile. The two constitute one Body of Christ, one true Israel of God, one nation of royal priests, one holy city, the new Jerusalem.