Paul continues to address mankind’s problem of sin here. He has not yet come to the solution. The fact that some people recognize sin and have an idea of the perfection required to be good is not enough to make those people good. The problem and evil described at the end of chapter one is apparent to many people. They see the bad direction people are headed in and want to correct it. They want morality and good living. The problem is that they think it can be achieved without acknowledging why things are so bad to begin with.
This is the goal of beliefs like Secular Humanism. Many atheists want morality in society in fact. The problem is that they are just as off the mark as people who practice evil. They do not recognize the Creator or their need for Him. The very act of judging the way they do—imposing a human ideal as good enough—is in itself a sin just like in chapter one. It is a way of placing creation in the role of creator.
Recognizing evil and a need to correct our ways is not enough. Not only that, but knowing about God and His requirements is also not enough. Paul says that people need to be doers and not just hearers. This would have been a strange statement for the Jews of Paul’s day. They assumed that simply being people of the law—those that had access to it, and knew it, and could hear it—made them God’s people. In a way, that is similar to the teaching of a lot of evangelicals today. We are so concerned that salvation be by faith and not works that we forget that people are saved to do good works. The teaching has devolved to the point that some people think you just need to believe that we are sinful and there is a God who has provided salvation and you are set. Not so. Knowing that there is sin and that there is a God is not enough.