These verses speak to us of the behavior Christians are to have in an ungodly world. The word walk is used of our life motives and the way we live. The rest of the world without the knowledge of Christ have their understanding darkened. Understanding speaks to me as more than just knowledge. I may have a lot of knowledge and not anything of understanding. What we need is understanding being enlightened. (Chapter 1:18) Then we will know what God wants. The ones Paul describes are alienated from the life of God. We should not walk that way. The above mentioned are described as past feeling and given over to all kinds of sin. Given over describes all kinds of sinful activity in Romans 1. There God is saying, "You want it have at it, but don't expect any blessing from me. I shudder at our own country today with gay marriage, abortion, sex without marriage etc. Paul now makes a simple phrase, "You have not so learned Christ, if so you have heard Him and are taught by Him, as the truth is in Jesus." Sad to me is people that come into the church with that kind of life style too.