I am not at present concerned to explore Paul’s general claim that those who deny the Creator are wicked but only his more particular claim that they are intellectually dishonest. Notice that he does not criticize nonbelievers because they do not know about God but ought to. Rather, he criticizes them because they do know about God but pretend to themselves that they don’t. According to his account, we are not ignorant of God’s reality at all. Rather, we “suppress” it; to translate differently, we “hold it down.” With all our strength we try not to know it, even though we can’t help knowing it; with one part of our minds we do know it, while with another we say, “I know no such thing.” From the biblical point of view, then, the reason it is so difficult to argue with an atheist—as I once was—is that he is not being honest with himself. He knows there is a God, but he tells himself that he doesn’t. How can a person explain how he reached new first principles? By what route could he have arrived at them? To what deeper considerations could he have appealed? If the biblical account is true, then it would seem that no one really arrives at new first principles; a person only seems to arrive at them. The atheist does not lack true first principles; they are in his knowledge already, though suppressed. The convert from atheism did not acquire them; rather, things he knew all along were unearthed.
– J. Budziszewski ( on Romans 1:18-21 in Why I Am a Christian: Leading Thinkers Explain Why They Believe)