4:20 In contrast to unsaved Gentiles, Christians' minds are no longer dark, they are no longer aliens from God, and their hearts are no longer hard and impure. They did not learn to follow Christ by the natural mental processes that customarily lead to the degradation of unsaved Gentiles. They learned to follow Him as His disciples from the gospel. "Usually we learn subjects, not persons; but the Christian's choicest lesson-book is his loveworthy Lord."173 4:21 "If indeed" (NASB) means "surely" (NIV, cf. 3:2). The Ephesian believers had received teaching about Christ and had learned to live in the sphere of His will. This is the truth in Jesus that is in view. Whenever Paul used the name of Jesus in Ephesians, as here, he drew attention to the death and resurrection of the Savior. He did so here to remind his readers of the essence of the gospel message as an incentive to live for Christ.