The cross was the centerpiece of Paul's theology.It wasn't merely one of Paul's messages; it was the message. He taught about other things as well, but whatever he taught was always derived from, and related to, the foundational reality that Jesus Christ died so that sinners would be reconciled to God and forgiven by God.
Theologian D. A. Carson writes of Paul, "He cannot long talk about Christian joy, or Christian ethics, or Christian fellowship, or the Christian doctrine of God, or anything else without finally tying it to the cross. Paul is gospel-centered; he is cross-centered."
From his first epistle to his final letter to Timothy, Paul kept the atoning death and resurrection of Jesus at the center of his teaching. He "resolved to know nothing ... except Jesus Christ and him crucified" (1 Corinthians 2:2).
Mahaney's Living the Cross-Centered Life is the bringing together of his The Cross Centered Life and Christ Our Mediator along with new material.