Paul’s aim here is to show us that the heathen wickedness which drew down the wrath of God from heaven in his own day and in our’s, is not a curse upon man’s simple ignorance.  He begins now to show at some length that man’s wickedness is entirely culpable because it is sin against light.  It is true, that the common light of nature and conscience do not reveal to us everything we need to know about God.  Nevertheless, if this is all the light God gives, and men rebel against it, then ought not God to hold them accountable for violating that which was evident to them?  There is much that may be known of God, the apostle tells us in verse 19.  It is manifest “in them,” which may perhaps be a reference to the conscience, which knows even apart from the written law that such crimes as murder, adultery, and stealing are wrong.  Or, as seems more likely in light of the immediately succeeding context, he may be referring to the light of nature, in which we see God’s glorious works of creation and providence.

In truth, these two things go together in some degree.  What we observe of God in the course of nature ought to affect our consciences, making us devout worshippers of our Creator, insofar as we are given light to know and understand Him and His character.  God has revealed much about Himself to us even apart from the supreme revelation of holy scripture.  There was a time when all the world knew about God as God, every family knowing as much as the other.  How could it be otherwise, when the sons of Noah each came off the ark, and each knew every thing about God in which their father could possibly instruct them?  How is it, then, that the vast majority of the tribes and nations descending from Shem, Ham, and Japheth, turned away from the true and living God to worship idols and revel in all sorts of uncleanness?  This passage supplies us with the clearest answer in all the word of God to that dilemma, and reveals very much to us about the darkness and wickedness of human nature.