Chapter 6 states “God created man upright and perfect, and gave him a righteous law, which had been unto life had he kept it, and threatened death upon the breach thereof.” What law was this? It was nothing less than God’s moral law that belongs to the nature and character of God. It is by this law in man at creation that Paul can say in Romans 1 that all men (unbelieving people) know God (Rom. 1:19, 21, 32). As a result they are without excuse (Rom. 1:20) and it’s just downhill from here in every respect.
God gives them over to their sin (vs. 24, 26, 28). They suppress the truth by their sin (vs. 18) They become futile in their minds and their hearts being foolish are darkened (vs. 21). They become idolaters by exchanging the glory of the incorruptible God for images (vs. 23). They exchange the truth about God for a lie and so worship the creature and no the Creator (vs. 25). They commit unnatural sexual sins (vv. 24, 26, 27). They are increasingly sinful (vv. 29 – 31). They approve the sins and sinning of others and do the same (vs. 32) End result: God’s wrath is upon them (vs. 18). So, if Adam had kept the law he would have entered life, but since he broke the law inherent within and commanded to him, he entered death, and thus sin came to all men and all die because all have sinned (Rom. 5:12). So, all know the truth but because sin reigns they continually spurn it and break it.