From the glorious heights of the heavenly places (Ephesians 1-3) to the promising potential of the church (Ephesians 4:1-16), Paul now descends to the reality of the sinful world.

The church is in this world, but this world must not be in the church. The believers in Ephesus were gathered by God into the redeemed church. They were to make a clean break with their past and no longer live like unbelievers (v. 17). Society in Ephesus and in the ancient Roman Empire was filled with spiritual darkness, moral impurity, and sexual immorality. It was an environment that was hostile to Christian living.

Worldly people have hardened hearts (v. 18) that are unable and unwilling to respond to God. This keeps them in spiritual ignorance. They are thus separated or alienated from God and His life, and do not understand truth. As a result, all their thoughts ultimately amount to nothing. The result of going down this ungodly path is that its travellers lose ″all sensitivity″ to the things required by God and give themselves over to ″sensuality″, or moral impurity and sexual immorality (v. 19). Bible commentator William Barclay points out that a licentious man ″does not care how much he shocks public opinion so long as he can gratify his desires″. What was true in Ephesus is also true today.

A follower of Christ must live a radically different kind of life (″That, however, is not the way of life you learned″, v. 20). Christians ″heard about Christ″ (v. 21) and were ″taught in him″ (v. 21). Christian education and intimacy with Christ help us to live differently. This involves putting off the old self and putting on the new self-a ″self transplant″.

The old self is the sinful nature, the instrument of our ″former way of life″ that is ″corrupted by its deceitful desires″ (v. 22). The new self is God's new creation of the regenerated self; it is ″created to be like God″ (v. 24). This new nature within us enables us to be holy and righteous as we trust in Christ and allow the Spirit to do His sanctifying work in us (1 Peter 1:2). Without this ″self transplant″ performed by God in us, we cannot live as Christians or live in heaven.