Healing prayer experiments and pigeons

Premier Christian Radio’s Unbelievable programme recently featured the atheist physicist Victor Stenger talking to the Christian statistician David Bartholomew about whether the failure of healing prayer experiments provides evidence against God’s existence. You can listen to the programme, and see some of the lively debates which occurred on Premier’s site, here and here. Bartholomew’s claim seems to be that these sort of experiments just can’t give any evidence about God, either for or against his existence. If the experiments had instead shown prayer did help with healing, he’d be among the people cautioning his fellow Christians not to draw any conclusion from it.

God is not a pigeon

So, why can’t experiments tell you anything about God? On the Premier forums, Tom Coverly summarises Bartholomew’s argument by saying that “God is a person, not a pigeon” (presumably a reference to Skinner’s experiments). But the objection that God is a person doesn’t seem to stand up: psychologists do useful experiments on people, after all, so God’s personhood alone can’t be the problem. Likewise, the fact that God knows every detail of the experiment isn’t necessarily a problem: not all experiments involving people can be done as blind trials (for instance, I suspect it’s pretty hard to come up with a placebo therapist when comparing antidepressant drugs to therapy).

The reason why scientists do healing prayer experiments in the first place is that Christians generally do claim that God answers prayers. They usually (though Coverly does not, as we’ll see) anticipate that some prayers are more likely to be answered than others: they might say that God is more likely to answer a prayer to heal a sick child than a prayer to give someone a brand new Ferrari. I’ll assume that Christians have some evidence for these beliefs. The claim that healing prayer experiments don’t provide evidence about God is then a rather strange one. Is this other evidence that the Christian has invalidated because they believe God is a person and that God knew he was providing the evidence? What makes the healing prayer experiments different?

Whatever can be destroyed by Bayes’ Theorem should be

Perhaps foreseeing this problem, Coverly claims that he does not think God is more likely to answer certain prayers than others, in fact, he says that humans cannot anticipate God’s actions at all. How should someone who agrees with Coverly bet on prayer experiments? How should an atheist bet? Suppose there are two outcomes: call healing the result that the prayers had a healing effect (after allowing for everything else), and no healing the result that the prayers had no effect. If we think that God exists but we cannot anticipate his actions, we should bet that the two are equally likely: after all, if we bet preferentially either way, we’re anticipating God’s actions (we could not bet, Coverly’s preferred option, but let’s suppose we have to bet, so we’d best minimise our losses). If we think that God doesn’t exist, we should bet strongly on no healing.

What this means is that the result no healing still provides more evidence for the claim that “God does not exist” than Coverly’s claim that “God exists but you can’t anticipate the result of prayers”. The claim that “God does not exist” is bolder: it sticks its neck out and says “you’ll certainly see no healing“, so that when no healing occurs (and it does), this claim is confirmed more strongly than the claim that which predicts you’ll see no healing about half the time. We can turn this into mathematics if we like, but that’s the gist of it.

Of course, there are other possibilities, such as “God exists but likes hiding from scientists more than healing sick people”, and in fact, this claim is confirmed over Coverly’s by our observations of no healing. Clearly, this area needs further research to differentiate the possible claims (for instance, we might investigate whether there is some threshold of seriousness for an illness, where God switches over to preferring healing to hiding from scientists): don’t ever let anyone tell you that you can’t learn anything about God from science.

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