I've seen it suggested that a team of people -- the more the better -- should agree to pray as hard as they knew how, over a period of six weeks, forall the patients in Hospital A and none of those in Hospital B. Then you would tot up the results and see if A had more cures and fewer deaths. . . .
The trouble is that I do not see how any real prayer could go on under such conditions. 'Words without thoughts never to heaven go', says the King in Hamlet. Simply to say prayers is not to pray; otherwise a team of properly trained parrots would serve as well as men for our experiment. You cannot pray for the recovery of the sick unless the end you have in view is their recovery. But you can have no motive for desiring the recovery of all the patients in one hospital and none of those in another. You are not doing it in order that suffering should be relieved; you are doing it to find out what happens. The real purpose and the nominal purpose of your prayers are at variance.
This is from a selection entitled Prayer is Not a 'Gimmick' in the Lewis Anthology The Business of Heaven(Nov. 14th), amidst a number of selections concerning prayer and the efficacy of prayer. I'm not sure what work of Lewis's this was originally taken from for the anthology.