Paul's theology is the main basis of Christian dogma.
First was the concept that the death and resurrection of Jesus superseded the value of the Mosaic Law, a belief that is often expressed as "Jesus died for our sins." It is unclear how much of this idea is original with Paul; Jerome notes the existence in the 4th century of a Christian sect in Syria called the Ebionites who still observed the Mosaic Law, thus suggesting at least some Christians may not have believed in the salvatory qualities of the Passion.
However, there is some evidence that suggests Paul's concept of salvation coming from the death of Jesus was not unique amongst Christians; Philippians 2:5-11 which expounds a Christology similar to Paul's, has long been identified as a hymn of the early Christians, and dated as existing before Paul's letter. Related to Paul's interpretation of the resurrection are his concepts of faith, which he explains through his explanation of Abraham, and of righteousness and the forgiveness for sins, using language that Augustine of Hippo later elaborated on in his formulation of original sin.
In the New Testament the doctrine of original sin is most clearly expressed by Paul's writings. His writings also clearly express the doctrine that salvation is not achieved by conforming to Mosaic law, but through faith in (or faith of) Jesus Christ. Paul was first Christians to expound the doctrine of Christ's divinity.
Paul also develops a strong doctrine of the Holy Spirit. Much of Romans and particularly the ending to 2 Corinthians portrays the Spirit in equality to the Father and Son. These inferences would later be developed into the doctrine of the Trinity. Paul's notion that the Holy Spirit dwells in all believers at the time of their conversion. (source Wikipedia)