From "Man or Rabbit?" by Clive Staples Lewis from the book God in the Dock: Essays on Theology and Ethics, Wm. B. Eerdmans Publishing Company
“Can’t you lead a good life without believing in Christianity?” This is the question on which I have been asked to write, and straight away, before I begin trying to answer it, I have a comment to make. The question sounds as if it were asked by a person who said to himself, “I don’t care whether Christianity is in fact true or not. I’m not interested in finding out whether the real universe is more what like the Christians say than what the Materialists (atheists) say. All I’m interested in is leading a good life. I’m going to choose beliefs not because I think them true but because I find them helpful.” Now frankly, I find it hard to sympathise with this state of mind.
...The question before each of us is not “Can someone lead a good life without Christianity?” The question is, “Can I?” We all know there have been good men who were not Christians; men like Socrates and Confucius who had never heard of it, or men like J. S. Mill who quite honestly couldn’t believe it. Supposing Christianity to be true, these men were in a state of honest ignorance or honest error. If there intentions were as good as I suppose them to have been (for of course I can’t read their secret hearts) I hope and believe that the skill and mercy of God will remedy the evils which their ignorance, left to itself, would naturally produce both for them and for those whom they influenced. But the man who asks me, “Can’t I lead a good life without believing in Christianity?” is clearly not in the same position. If he hadn’t heard of Christianity he would not be asking this question. If, having heard of it, and having seriously considered it, he had decided that it was untrue, then once more he would not be asking the question. The man who asks this question has heard of Christianity and is by no means certain that it may not be true. He is really asking, “Need I bother about it?” Mayn’t I just evade the issue, just let sleeping dogs lie, and get on with being "good”? Aren’t good intentions enough to keep me safe and blameless without knocking at that dreadful door and making sure whether there is, or isn’t someone inside?”
To such a man it might be enough to reply that he is really asking to be allowed to get on with being “good” before he has done his best to discover what good means. But that is not the whole story. We need not inquire whether God will punish him for his cowardice and laziness; they will punish themselves. The man is shirking. He is deliberately trying not to know whether Christianity is true or false, because he foresees endless trouble if it should turn out to be true. He is like the man who deliberately “forgets” to look at the notice board because, if he did, he might find his name down for some unpleasant duty. He is like the man who won’t look at his bank account because he’s afraid of what he might find there. He is like the man who won’t go to the doctor when he first feels a mysterious pain, because he is afraid of what the doctor might tell him.
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