As you read, consider how God describes his self-revelation:
18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. 19 For what can be known about God is plain to them, because God has shown it to them. 20 For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse. 21 For although they knew God, they did not honor him as God or give thanks to him, but they became futile in their thinking, and their foolish hearts were darkened. 22 Claiming to be wise, they became fools, 23 and exchanged the glory of the immortal God for images resembling mortal man and birds and animals and creeping things.
“In the opening chapter of his letter to the Romans, especially verses 18–32, it is noteworthy that the whole framework of the passage is the objective nature of things. William Barclay observes that Paul does not speak of God’s being angry, but of the wrath of God as a fact.1 The parallel is that the witness to God is there, objectively, apart from the human response to it.
Paul seems to emphasize the reality and clarity of the witness. Thus, if there is a failure of knowledge, the problem appears not to lie with the witness itself. In Romans 2:14–16 the locus is quite different. Rather than being located in the external, created world, Paul here emphasizes the human heart. Referring to those who do not have the law, presumably the law revealed in the Old Testament, he speaks of those who nonetheless do the things required by the law (v. 14). He says that by so doing, they show that “the requirements of the law are written on their hearts” (v. 15). It appears Paul is asserting that God has left some witness within the human moral makeup of his requirements for them.”
1. William Barclay, The Epistle to the Romans (Philadelphia: Westminster, 1975), 24–28.
Erickson. God’s Universal Revelation. Introducing Christian Doctrine (p. 28). Baker (2015)