Despite the exponential growth of medical information, the effects of healthcare interventions are often uncertain or controversial.^w1 This unreliability or uncertainty of all information is what the military philosopher Clausewitz called the fog of war.1 Clausewitz maintained that the key to a rational approach to warfare was understanding the impact of chance and the laws of the probability and its interplay with the other factors in war—such as people, governments, and, in particular, the commander in the field. This approach may also benefit health care.

Recently, McNeil argued that the major hidden barriers to better health care result from a lack of discussion of the impact of uncertainty in medicine.2 She enumerated several sources of uncertainty that cloud decision making in modern health care: uncertainty as a result of lack of convincing evidence because of delayed or obsolete data from clinical studies; uncertainty about applicability of evidence from research at the bedside; and uncertainty about interpretation of data.2 ^w2 Others …