The lesson begins with the claim that the existence of God is self-evident. The heavens are telling of the glory of God, and day after day creation speaks without words to the ends of the earth. Paul adds that what can be known about God is plain to all, because God has made it evident: His eternal power and divine nature are clearly seen in what He has made, so that people are without excuse.
Why then do people deny Him? The study answers that the root is moral, not intellectual. People suppress the truth in unrighteousness because they know they are accountable to a holy God, and so they try to silence Him and put Him out of the picture. The fool says in his heart there is no God. Since the fall, human thought has made man the measure of reality, but Jesus warns that those who do not believe in Him will die in their sins.