In 2009, on a grant from the John Templeton Foundation, the Browns flew to Mozambique to investigate the healing claims of Global Awakening and Iris Global, two ministries focused on healing and revival. They brought audiometry equipment and eye charts to test people who requested prayer for deafness and blindness. The sample size was small — they tested 24 people — but they found statistically significant improvement beyond placebo effects and hypnosis.

“I was standing right there next to this woman who could not tell how many fingers were held up when you were a foot in front of her,” Candy Brown told me. “Then five minutes later, she’s reading an eye chart with a smile on her face.” She and her colleagues published the results in The Southern Medical Journal — not a prestigious publication but a respectable one with peer review — and she drew on the research for her 2012 book, “Testing Prayer.”

Skeptics complained about the Browns’ methods and field conditions. They pointed out that the hearing tests were in a noisy setting, there was no control group and test subjects would naturally want to please those who prayed for them by showing results. “That simple trick explains why both hearing and sight appears to have dramatically improved among these poor, superstitious villagers,” one critic declared. (The study explained in detail how the researchers did their best to weed out false data.)

If you want to evaluate people’s experiences at a revival in rural Africa, you probably need to give up on double-blind studies in a perfectly controlled environment. But let’s imagine for a moment that researchers could meet such standards (and that an all-powerful deity humors us and submits to this scrutiny). They might persuade skeptics that something strange happened. But is there any evidence that would persuade a nonbeliever that God was behind it — that we do not live in a closed system in which all causation is a matter of natural laws?