I have declared to both Jews and Greeks that they must turn to God in repentance and have faith in our Lord Jesus. – Acts 20:21 NIV
While I know that this was not all that Paul taught, it was at the center of his proclamation. Theology is good and helpful for growing in our knowledge of God, and Paul gave us a lot of theology. Apologetics is also good, helping us to give answer to those who ask why we believe (1 Peter 3:15-16). But evangelism, proclaiming the good news of Jesus Christ, is essential for reaching the lost world around us. And at the heart of the gospel is this call to turn to God in repentance, and trust your life to the lordship of Jesus. It is a call to surrender.