- "Jesus is Lord" - Paul refers to Jesus as Lord frequently. This had both religious and sociopolitical meanings. He was affirming that the "risen Christ" participated in the power and authority of God. He was also affirming that since "Jesus is Lord", "Caesar is not Lord".
- "In Christ" - Paul uses this phrase (or "in the Lord") 165 times. He uses it to refer to being free, no longer enslaved to the dominion of sin and death...characterized by things like freedom, love, joy, peace, patience, kindness, generosity, faithfulness and self-control. Life "in Christ" also has a social dimension in that it negates the social boundaries that mark conventional human existence.
- "Justification by Grace" - Paul contrasts justification by works of the law with justification by grace through faith. Justification is a free gift, not a reward for achievement. In Galatians, for example, justification by grace through faith is the basis for Gentiles becoming part of the community without becoming Jewish through circumcision. Similarly, he makes this point in Romans. For Paul, justification by grace is the basis for our relationship to God...it is a gift of God, not a human accomplishment.
- "Christ Crucified" - Paul attaches various meanings to this including that Christ was crucified; an indictment of the rulers of the age who crucified Christ; a revelation of God's love for us; and a symbol of the path of transformation.
The New Testament doesn't tell us about Paul's death, but according to early Church tradition, he was believed to have been executed in the 60s. If so, it is interesting that Christianity's two most formative figures were executed by established authority.
Note: most of the above was taken from Marcus Borg's Reading the Bible Again for the First Time.