What does it mean to be a Christian? And what does it mean for a group of Christians to form the church? William Barclay answers these two questions in his commentary on Ephesians 1:15-23. He writes:
Here, there is set out before us in a perfect summary the characteristics of a true church. Paul has heard of their faith in Christ and their love to all God’s consecrated people. The two things which must characterize any true church are loyalty to Christ and love to other people.
There is a loyalty to Christ which does not result in love to others. The monks and hermits had a loyalty to Christ which made them abandon the ordinary activities of life in order to live alone in the desert places. The heresy-hunters of the Spanish Inquisition and of many other periods of history had a loyalty to Christ which made them persecute those who thought differently from them. Before Jesus came, the Pharisees had a loyalty to God which made them contemptuous of those whom they thought less loyal than themselves.
True Christians love Christ and they also love their neighbors. More than that, they know that they cannot show their love to Christ in any other way than by showing their love to their neighbors. However orthodox a church is, however pure its theology, and however noble its worship and its liturgy, it is not a true church in the real sense of the term unless it is characterized by love for other people. There are churches which seldom make any public pronouncement which is not based on censorious criticism. They may be orthodox, but they are not Christian. The true Church is marked by a double love—love for Christ and love for others.