A book often suggests its theme by the words it repeats, called “key words.” In Ephesians the word “one” stands out as a key word.1 After introducing the wonders of God’s choice and our adoption, Paul launches his theme of unity on a grand scale:
…making known to us the mystery of his will, according to his purpose, which he set forth in Christ as a plan for the fullness of time, to unite all things in him, things in heaven and things on earth (Ephesians 1:9-10).2