The leader of the experiments, Professor Russell Stannard of the Open University, is keeping an open mind on what might result: "God's got a will of His own and might decide not to co-operate."
The tests - funded by the John Templeton Foundation, a charitable organisation aimed at the progress of religion - will involve three groups of 600 patients awaiting heart surgery.
Two groups will be told they may be prayed for by a special praying team; one actually will be prayed for, the other will not, but neither will know for certain which group is in the team's thoughts.
A third group will know they are being prayed for and will be monitored to determine if that knowledge has a psychosomatic effect on their symptoms.
Professor Stannard, who has given the financial go-ahead for the project to be conducted at three American hospitals over two years, said its purpose was merely "to find out what happens".
"The foundation is not going into the experiment hoping that there will be a positive effect. We are genuinely interested in any experimentation which has a bearing on religion," said Professor Stannard.
"Obviously, if it turns out that there is a positive result, that will be extremely interesting.
"It would open up whole areas of research, such as different methods of prayer, and prayer for different illnesses."
Professor Stannard, who sees no contradiction in being both a Christian and a scientist, said a result showing no significant difference between the groups would not necessarily prove prayer did not help. He said people might pray for themselves and receive prayers from close friends and family, unaccounted-for prayer known scientifically as "unwanted background noise".
As well as God proving problematic by not co-operating with the experiment, Professor Stannard said there could also be trouble if there is divine intervention and it was proved that prayer was successful.
"If we find prayer does work, then we get into the area of asking: How much does this work?" he said. "As soon as you get into that quantitative area, you put a price on it."
Prayer could then, the professor suggested, be equated with hospital treatment, with vicars instead of health trust managers being called on to justify the closure of hospital wards.
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