Where is this C.S. Lewis quote from? Talking to a friend, he wrote:


  In the words (approximate) of C.S. Lewis, "Everytime a man sleeps with a woman, it creates a bit more of a spiritual connection that must be either eternally enjoyed or eternally endured."


This sounds like Lewis - but where is it from?
It's from The Screwtape Letters, letter XVIII.


  The truth is that wherever a man lies with a woman, there, whether they like it or not, a transcendental relation is set up between them which must be eternally enjoyed or eternally endured.


In context, Screwtape is telling Wormwood that the "one flesh" analogy in the Bible refers not to some romantic notion of "being in love," but rather to copulation itself. Of course, Screwtape, being a demon, is admonishing Wormwood that he can help people "forget" such things in order to give in to their desires of the flesh.