"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" (v. 21).
God has revealed Himself so clearly in the natural order that no person will ever be able to stand before the Creator and claim that there is insufficient evidence that He exists and should be worshiped. We have already seen how the Bible teaches this in texts such as Psalm 19, and today's passage makes the point with even greater forcefulness. As Paul says in Romans 1:20, God's "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."
Romans 1:18–32 proclaims not only that the Lord has plainly revealed Himself in nature, but it also tells us that there are certain limits to natural revelation. To put it simply, we receive enough truth about God in natural revelation to know that He is there; however, we do not receive enough information to be saved. In fact, Paul tells us that when sinners come into contact with God's revelation of Himself in nature, they suppress the truth they have received. Without faith in Christ, when fallen people study God's creation, they become futile in their thinking and their hearts are darkened. They do not honor the Lord or give thanks to Him (v. 21). What is more, they exchange the truth that they have seen in the created order for a lie—they engage in all manner of false religion and idolatry, worshiping the creature rather than the Creator (vv. 22–25). In sum, sinners who encounter natural revelation apart from grace and God's revealing His plan of salvation make God in their own image, and they refuse to worship the only Lord of all.
The idolatry that results when people receive natural revelation is not the fault of natural revelation. Instead, it is the fault of the sin that pervades fallen human beings. Natural revelation is insufficient for salvation, but God never intended it as a means of salvation. Instead, as Paul explains in Romans 1–3, the point of natural revelation is to show people truth about the Lord so that they can see the truth about themselves, namely, that they are sinners in need of salvation. But it takes more than natural revelation in order for people to be redeemed. For that, they need special revelation, the truth about God's work in history—preeminently in the person and work of Jesus Christ—that are available only via our Lord's speaking directly to His people and revealing to them truths that nature does not teach. Today, this special revelation is available only in Scripture.
Coram Deo
We can appeal to natural revelation to show people certain truths about God's character and even to prove that they have violated the moral law that He has placed on the consciences of all people. However, no one will be saved only by looking at natural revelation. We must preach the gospel—give men and women the truths of special revelation—or they cannot be saved from the wrath of God.