Man or Rabbit

In this section of Lewis’s Man or Rabbit? Lewis tackles the question ‘Can’t you lead a good life without Christianity?’. First off, he makes a distinction between those who know about Christianity and those who do not know. Obviously, Lewis says, one who is posing such a question knows about Christianity because they are asking about it. One who does this is looking for a religion of convenience. They want to find out whether Christianity will bring them happiness in the end and if it is worth the effort needed to be put into it. He ends by saying that ultimately, those who know about Christianity and reject it cannot live a good life. The last sentences really sum up his idea on the matter. “Morality is a mountain which we cannot climb by our own efforts; and if we could we should only perish in the ice and unbreathable air of the summit, lacking those wings with which the rest of the journey has to be accomplished. For it is from there that the real ascent begins. The ropes and axes are ‘done away’ and the rest is a matter of flying.” Without Christianity, we cannot climb to the top of the mountain of morality, and even if it were possible, we would not have the wings to fly up and ascend from it.
I did have a question about this, however. Lewis makes a distinction from those that know about Christianity and those that don’t. What exactly is his opinion of those that do not “know”? This idea made me think of Romans 1: 18-21 “For since the creation of the world His invisible attributes are clearly seen, being understood by the things that are made, even His eternal power and Godhead, so that they are without excuse, because, although they knew God, they did not glorify Him as God, nor were thankful, but became futile in their thoughts, and their foolish hearts were darkened.” If my interpretation of this verse is correct, there are not any that simply “don’t know.”