prayer, correlation, and causation

Scientists are typically sceptical of the claim that because some event Y follows some event X, it therefore follows that X causes Y. And for good reason.

Correlation, they say, does not imply causation. Even where two events are “constantly conjoined” one may not be the cause of the other. (A dropping barometer, for example, may always precede bad weather, but the barometer’s actions do not cause weather changes.)

Accordingly, scientists have devised increasingly sophisticated techniques to distinguish  true causation from  mere random coincidence. Statistical analysis can help isolate minor contributory causes. Double blind studies can guard against observer bias and subject’s expectations.  The use of control groups can detect whether a change is due to the independent variable being tested or some other factor which observers may have neglected. Simulated treatment can help control for the placebo effect. Peer review can detect cases of investigator fraud. Replication of reported results can distinguish between real phenomena and observer error. And so on. None of this is easy and scientists have frequently to change their commitments as new evidence undermines the validity for formerly respected beliefs.

This is nowhere so true, and so humanly important, as in the case of medical research. John Iloannis, for example, reviewed the 49 most-cited peer-reviewed medical journal, articles – what one might describe as the gold standard of medical research – and found that fully a third of them to have been shown faulty.

But this hardly implies that we ought to abandon medical science, or science itself, as a useful tool to understand the natural world. As Iloannis himself puts it,

Science is a noble endeavor, but it’s also a low-yield endeavor… I’m not sure that more than a very small percentage of medical research is ever likely to lead to major improvements in clinical outcomes and quality of life. We should be very comfortable with that fact.

Nonetheless, many people are unhappy with the constraints thus imposed by science and the almost insurmountable difficulties they present for people  determined to find “scientific proof” for some pet theory or other.

Consider, for example, the oft-cited study on the effect of of intercessionary prayer on three matched groups of heart patients: one group was prayed for but didn’t know, another group was not prayed for but didn’t know and third group knew it was being prayed for.

The results are stunning:

Intercessory prayer itself had no effect on complication-free recovery from CABG, but certainty of receiving intercessory prayer was associated with a higher incidence of complications.

So praying itself is harmless enough but saying, “I’ll pray for you,” is not likely to help those afflicted with heart disease.

There are two widely-used responses to studies such as these:

1. Prayer is effective, but it is not a mechanical means to manipulate God into giving us whatever we want. God gives us what we need, not what we want or expect. So that’s why studies don’t show clear evidence of God’s intervention.

Petty obviously, to make this  objection scientifically respectable, we need to see some independent evidence that God actually does answer prayers oppositely to what we ask for. Otherwise, this move effectively removes God’s influence from empirical observation, since any outcome from prayer whatsoever could be interpreted as God’s response. In short, God’s handiwork becomes indistinguishable from mere natural causes.

2. Though the studies don’t confirm it, we can know that prayer is effective, since desirable (and sometimes unexpected) results follow prayer. This approach is usually accompanied by (1) ignoring cases where prayer doesn’t work and (2) ignoring the effects of purely natural causes (such as medical intervention).

But there are good reasons why believers in prayer should not assume that unexpected events that follow prayer are actually the results of prayer. Here’s why.

This graph shows the percentage area of Texas land under D4 (“extreme”) drought conditions for the last ten years, as measured here. Note the huge spike at the right hand side. Plainly something occurred in the spring of 2011 to cause a drought without precedent in the last decade. So let’s zoom in that time period.

As you can see, prior to the end of March 2011, no part of Texas is listed as D4. By  the 19th of April, 15% is listed D4. And on the 21st of April, Texas Governor Rick Perry notices this and issues a proclamation calling for three days of state prayer 22-24 April in an effort to end the drought. I’ve indicated that day with the yellow arrow above.

And the D4 area shoots like a rocket up to almost 80%. Exactly opposite to Perry’s desired result. Now, if you really wanted to avoid the conclusion that God doesn’t answer prayer, you could conclude that this destructive  and widespread drought was actually God’s answer to Perry’s prayer, no matter what devoutly Christian Texans wanted.

Or you could instead reach another strikingly non-supernatural conclusion about the cause of the drought:

Q: What is causing the drought in 2011?
A: A lack of rain, caused by a strong La Niña weather pattern that started in late 2010.


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