Why

Chapter 4. Time

How does time affect our ability to perceive and reason with causality?

A randomized controlled trial conducted in 2001 tested whether prayer could improve patient outcomes, such as reducing how long patients were in the hospital.¹ The double-blind study (neither doctors nor patients knew who was in each group) enrolled 3,393 adult hospital patients who had bloodstream infections, with approximately half assigned to the control group and half to the prayer intervention group. Of the measured outcomes, both length of hospital stay and fever were reduced in the intervention group, with the difference being statistically significant (p-values of 0.01 and 0.04).

Yet if this intervention is so effective, why aren’t all hospitals employing it? One reason is that the patients in this study were in the hospital from 1990 to 1996—meaning that the prayers for their recovery took place long after their hospital stays and outcomes occurred. In fact, the prayers were not only retroactive, but also remote, occurring at a different place and time and by people who had no contact with the patients.

A cause affecting something in the past is completely contrary to our understanding of causality, which usually hinges on causes preceding their effects (if not being nearby in time as well) and there being a plausible physical connection linking cause and effect. Yet the study was conducted according to the usual standards for randomized trials (such as double blinding) and the results ...