God's Righteous Judgment

The writer of this letter was the apostle Paul. The original recipients of the letter were the people of the church at Rome, who were predominantly Gentile

6 God "will give to each person according to what he has done."
7 To those who by persistence in doing good seek glory, honor and immortality, he will give eternal life.
8 But for those who are self-seeking and who reject the truth and follow evil, there will be wrath and anger.
9 There will be trouble and distress for every human being who does evil: first for the Jew, then for the Gentile;
10 but glory, honor and peace for everyone who does good: first for the Jew, then for the Gentile.
11 For God does not show favoritism.
12 All who sin apart from the law will also perish apart from the law, and all who sin under the law will be judged by the law.  
13 For it is not those who hear the law who are righteous in God's sight, but it is those who obey the law who will be declared righteous.  
14 (Indeed, when Gentiles, who do not have the law, do by nature things required by the law, they are a law for themselves, even though they do not have the law,  
15 since they show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts now accusing, now even defending them.)  
16 This will take place on the day when God will judge men's secrets through Jesus Christ, as my gospel declares.  
Romans 2 (New International Version)

Who was Paul?
At the age of fourteen Paul was sent to Jerusalem to train to be a Rabbi.
Paul grew to be a man of firm convictions and fiery temperament. He always acted on his beliefs. Thus, when he was confronted with what he took to be a heresy to Judaism, he worked with all his might to quell it. This heresy would one day come to be known as Christianity and Paul was among the foremost of its persecutors.
He then undertook a mission to Damascus. There he intended to continue attacking Christians. However, on the way, he had a vision. This vision is described several times in the Bible, three times in the book of Acts. Paul saw Jesus who asked why Paul persisted in persecuting Him. He then commissioned Paul to preach His message to the Gentiles.

What is "the law"?