The question then arises, "What sort of evidence would prove the efficacy of prayer?" The thing we pray for may happen, but how can you ever know it was not going to happen anyway? Even if the thing were indisputably miraculous it would not follow that the miracle had occurred because of your prayers. The answer surely is that a compulsive empirical proof such as we have in the sciences can never be attained.
Some things are proved by the unbroken uniformity of our experiences. The law of gravitation is established by the fact that, in our experience, all bodies without exception obey it. Now even if all the things that people prayed for happened, which they do not, this would not prove what Christians mean by the efficacy of prayer. For prayer is request. The essence of request, as distinct from compulsion, is that it may or may not be granted. And if an infinitely wise Being listens to the requests of finite and foolish creatures, of course He will sometimes grant and sometimes refuse them. Invariable "success" in prayer would not prove the Christian doctrine at all. It would prove something much more like magic -- a power in certain human beings to control, or compel, the course of nature.
There are, no doubt, passages in the New Testament which may seem at first sight to promise an invariable granting of our prayers. But that cannot be what they really mean. For in the very heart of the story we meet a glaring instance to the contrary. In Gethsemane the holiest of all petitioners prayed three times that a certain cup might pass from Him. It did not. After that the idea that prayer is recommended to us as a sort of infallible gimmick may be dismissed.
Other things are proved not simply by experience but by those artificially contrived experiences which we call experiments. Could this be done about prayer? I will pass over the objection that no Christian could take part in such a project, because he has been forbidden it: "You must not try experiments on God, your Master." Forbidden or not, is the thing even possible?
I have 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, for all 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. And I suppose you would repeat the experiment at various times and places so as to eliminate the influence of irrelevant factors.
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 experiments. 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. In other words, whatever your tongue and teeth and knees may do, you are not praying. The experiment demands an impossibility.
Empirical proof and disproof are, then, unobtainable. But this conclusion will seem less depressing if we remember that prayer is request and compare it with other specimens of the same thing.
For up till now we have been tackling the whole question in the wrong way and on
the wrong level. The very question "Does prayer work?" puts us in the wrong frame
of mind from the outset. "Work": as if it were magic, or a machine -- something that
functions automatically. Prayer is either a sheer illusion or a personal contact
between embryonic, incomplete persons (ourselves) and the utterly concrete
Person. Prayer in the sense of petition, asking for things, is a small part of it;
confession and penitence are its threshold, adoration its sanctuary, the presence
and vision and enjoyment of God its bread and wine. In it God shows Himself to us.
That He answers prayers is a corollary -- not necessarily the most important one -- from that revelation. What He does is learned from what He is.
"The Efficacy of Prayer"
The World's Last Night and Other Essays