A promising line is the following. Now that he is in love, a new idea of earthly happiness has arisen in his mind: and hence a new urgency in his purely petitionary prayers-about this war and other such matters. Now is the time for raising intellectual difficulties about prayer of that sort. False spirituality is always to be encouraged. On the seemingly pious ground that ‘praise and communion with God is the true prayer’, humans can often be lured into direct disobedience to the Enemy who (in His usual flat, commonplace, uninteresting way) has definitely told them to pray for their daily bread and the recovery of their sick . . .
But since your patient has contracted the terrible habit of obedience, he will probably continue such ‘crude’ prayers whatever you do. But you can worry him with the haunting suspicion that the practice is absurd and can have no objective results. Don’t forget to use the ‘heads I win, tails you lose’ argument. If the thing he prays for doesn’t happen, then that is one more proof that petitionary prayers don’t work; if it does happen, he will, of course, be able to see some of the physical causes which led up to it, and ‘therefore it would have happened anyway’, and thus granted prayer becomes just as good a proof as a denied one that prayers are ineffective. (1)
This is exactly what I have been struggling with the past two or three years. I completely forgot that Lewis already saw this himself.
(1) Lewis, Clive S. The Screwtape Letters. New York: HarperOne, 1996. 147-148. Print.