What was the central concern of Christianity according to the Apostle Paul?

Answer 1

From the letters of Paul we can see that the central concern he had was believers deviating from the truth of the gospel. Many of his letters are written to correct wrong practice.

For the Jewish Christians the main error was returning to the Law of Moses. For the non Jewish Christians the error was getting pursuaded to start keeping the Law of Moses

Galatians 3:1 O foolish Galatians! Who has bewitched you that you should not obey the truth, before whose eyes Jesus Christ was clearly portrayed among you as crucified?

Another View:

It would seem Paul wanted to insure the new gentile converts knew they did not have to be 'Jews' to have God's Salvation - His free gift to all mankind now. Some Jews were pressuring the new converts to be like them so they could be incorporated into Judaism. This was not what God wanted and Paul wrote in many letters that the new gentiles did not have to become Jews. He wanted them to understand that the Law of Moses was still in place, however, parts of this law they did not have to follow namely the sacrificial and ceremonial part of the Law of Moses - established about 1 year after Mt. Sinai and the Commands of God - to help the Hebrews remember God and His expectations of His Chosen/Church in the Wilderness. Paul's Letter to the Hebrews addresses this extensively:

Hebrews 9:9-10New English Translation (NET Bible) 9 This was a symbol for the time then present, when gifts and sacrifices were offered that could not perfect the conscience of the worshiper. 10 They served only for matters of food and drink and various washings; they are external regulations imposed until the new order came.

Paul insured all kept the Law of Moses just like Jesus did - excluding these ceremonial (Jesus born as a Jew kept the ceremonial rituals only) and sacrificial laws - making an Administrative adjustments for our new Eternal High Priest, Jesus Christ, our only mediator to the Father. The Levitical priesthood was no longer needed. Paul expressed this cleary in his letter to the Romans - predominantly for gentiles:

Romans 3:28-31New English Translation (NET Bible) 28 For we consider that a person is declared righteous by faith apart from the works of the law. 29 Or is God the God of the Jews only? Is he not the God of the Gentiles too? Yes, of the Gentiles too! 30 Since God is one, he will justify the circumcised by faith and the uncircumcised through faith. 31 Do we then nullify the law through faith? Absolutely not! Instead we uphold the law.

And this is what Paul was speaking to the Galatians and Corinthians about as well. The main topic became whether or not to be circumcised to be symbolically like the Jews as they were pushing for the Galatians to take on their customs:

1 Corinthians 7:19New English Translation (NET Bible) 19 Circumcision is nothing and uncircumcision is nothing. Instead, keeping God's commandments is what counts.

Note: the Commands of God are in the Law of Moses predominantly!!

Galatians 5:3New English Translation (NET Bible)

"3 And I testify again to every man who lets himself be circumcised that he is obligated to obey the whole law." So the question becomes, was Paul implying here that the new gentile converts, having the exemption from physical 'circumcision' were also exempt from having to obey any of the laws of God? (see Romans 3:28-31 above once again).

Unfortunately, many in Christendom teach the abolishment of the Law of Moses. This is totally incorrect and if Paul were here now, he would strive to correct this error just like he did during his missionary works to the various cities of which he wrote.