According to Lewis "Going back is the quickest way on." Now, let me explain what he means. This is chapter five, and we are continuing our discussion of the Moral Law, and its Lawgiver.
We all want progress. But progress means getting nearer to the place where you want to be. And if you have taken a wrong turning, then to go forward does not get you any nearer.
We have two bits of evidence about the Somebody. One is the universe He has made.... The other is that Moral Law which He puts into our minds. And this is a better bit of evidence than the other, because it is inside information.
This is the terrible fix we are in. If the universe is not governed by an absolute goodness, then all our efforts are in the long run hopeless. But if it is, then we are making ourselves enemies to that goodness every day, and are not in the least likely to do any better tomorrow, and so our case is hopeless again. We cannot do without it, and we cannot do with it. God is the only comfort, He is also the supreme terror: the thing we most need and the thing we most want to hide from. He is our only possible ally, and we have made ourselves His enemies.
Goodness is either the great safety or the great danger - according to the way you react to it. And we have reacted the wrong way.
Christianity tells people to repent and promises them forgiveness. It therefore has nothing (as far as I know) to say to people who do not know they have done anything to repent of and who do not feel that they need any forgiveness. It is after you have realized that there is a real Moral Law, and a Power behind the law, and that you have broken that law and put yourself wrong with that Power - it is after all this, and not a moment soon, that Christianity begins to talk.
When you have realised that our position is nearly desperate you will begin to understand what the Christians are talking about. They offer an explanation of how we got into our present state of both hating goodness and loving it. They offer an explanation of how God can be this impersonal mind at the back of the Moral Law and yet also a Person. They tell you how the demands of this law, which you and I cannot meet, have been met on our behalf, how God Himself becomes a man to save man from the disapproval of God.
Source: Mere Christianity c. 1952 C.S. Lewis