When sickness strikes, people around the world pray for healing. Many of the faithful claim that prayer has cured them of blindness, deafness and metastasized cancers, and some believe they have been resurrected from the dead.

Can, and should, science test such claims? A number of scientists say no, concerned that empirical studies of prayer will be misused to advance religious agendas. And some religious practitioners agree with this restraint, worrying that scientific testing could undermine faith.