Here by the way is another piece by Craig in which he maintains that atheists know God exists and, by the end of their lifetime, also the great truths of the Gospels.
Notice that Craig talks below about how God reveals himself in nature, but also that nature provides "evidence".
Is the idea that atheists can just see that God exists, as they look upon nature? Or is it that they should merely infer God's existence on the basis of evidence that nature furnishes? If the latter, then they don't necessarily know God exists - they may fail to spot the evidence or make the inference. And why is infinite punishment an appropriate penalty for failing to spot evidence or draw the right conclusions? Inattentiveness and logical error don't merit infinite punishment, surely?
Craig appears to endorse Paul, who says that God's existence is manifest in nature, even to the atheist, who thus does know God exists, and thus is without excuse. Plus there is the inner witness of the Holy Spirit drawing the atheist to knowledge of God (though this suggests the Holy Spirit might fail in this project, and thus the atheist might not come to know God exists by that route).
Craig posts a letter in which he is asked:
Dear Dr. Craig,
I am a brazilian Christian. Your work for the kingdom has been a tremendous help to me in my spiritual life.
I believe God exists, but I am troubled with a question.
Christians are supposed to think that God will punish atheists for choosing not to believe. But how can an sincere atheist be blamed for not believing?
I find that contemporary atheists take great umbrage at the biblical claim that God holds people to be morally culpable for their unbelief. They want to maintain their unbelief in God without accepting the responsibility for it. This attitude enables them to reject God with impunity.
Now we can agree that a person cannot be held morally responsible for failing to discharge a duty of which he is uninformed. So the entire question is: are people sufficiently informed to be held morally responsible for failing to believe in God? The biblical answer to that question is unequivocal. First, God has provided a revelation of Himself in nature that is sufficiently clear for all cognitively normal persons to know that God exists. Paul writes to the Roman church:
The wrath of God is being revealed from heaven against all the godlessness and wickedness of people, who suppress the truth by their wickedness, since what may be known about God is plain to them, because God has made it plain to them. For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that people are without excuse. For although they knew God, they neither glorified him as God nor gave thanks to him, but their thinking became futile and their foolish hearts were darkened (Rom. 1. 18-21).In Paul’s view God’s properties, His eternal power and deity, are clearly revealed in creation, so that people who fail to believe in an eternal, powerful Creator of the world are without excuse. Indeed, Paul says that they actually do know that God exists, but they suppress this truth because of their unrighteousness. As result they become so clouded in their thinking that they may actually deceive themselves into thinking that they are open-minded inquirers honestly pursuing the truth. The human capacity for rationalization and self-deception, I’m sure we’ve all observed, is very great, indeed, and in the biblical view atheists are prey to it.
Second, wholly apart from God’s revelation in nature is the inner witness which the Holy Spirit bears to the great truths of the Gospel, including, I should say, the fact that God exists. Anyone who fails to believe in God by the end of his lifetime does so only by a stubborn resistance to the work of the Holy Spirit in drawing that person to a knowledge of God. On the biblical view people are not like
innocent, lost lambs wandering helplessly without a guide. Rather they are determined rebels whose wills are set against God and who must be subdued by God’s Spirit.