Ephesians is one of Paul's most profound epistles, focusing on the cosmic nature of the church as the body of Christ and the unity of Jews and Gentiles in one people of God. The letter reveals God's eternal purpose for humanity, the spiritual riches available in Christ, and the practical implications of living as citizens of the heavenly kingdom. Paul emphasizes God's grace, Christ's unifying work, and the need for mature Christian living that reflects the transformative nature of the gospel.