Paul's contrast between former spiritual death in trespasses and sins and present spiritual life in Christ emphasizes that salvation is entirely by grace through faith, not human works, to prevent boasting. The second half demonstrates how the cross breaks down the wall of hostility between Jews and Gentiles, creating one new humanity with equal access to the Father through the Spirit. The metaphor of believers as God's temple being built on the foundation of apostles and prophets with Christ as the cornerstone shows how individual salvation serves corporate purposes.