Those spiritually dead live "according to the course of this world, according to the prince of the power of the air, the spirit who now works in the sons of disobedience" (Ephesians 2:2). The spiritually dead have no faith in Christ. Another spirit works in them, the spirit of disobedience. Their lifestyle is according to this present evil world. The spiritually dead have no personal relationship with God.
God makes the spiritually dead alive in our Lord Jesus Christ. "But God, who is rich in mercy, because of His great love with which He loved us, even when we were dead in trespasses, made us alive together with Christ" (Ephesians 2:4-5). We receive new life from the mercy and love of God for us in Christ. Because Christ lives, we are spiritually alive to God. Christ is our new life.
What did we do to deserve new life with God? The answer is nothing. It's because of God's mercy toward us. It is God's mercy and grace through faith in Christ alone. We were spiritually dead, but now "by grace you have been saved" (Ephesians 2:5). By grace through faith in Christ, we are spiritually alive to God.
Those spiritually dead are made alive by the mercy of God through the gospel of Christ. Before we trusted in the Lord Jesus Christ, we were spiritually dead. The word dead means separated. We were spiritually dead, that is separated from God. "And He made you alive, who were dead in trespasses and sins" (Ephesians 2:1).