The privatization, or individualization, of risk factor knowledge has been largely responsible for a rising tide of criticism of epidemiology. The current debate seems polarized into 2 sides, those who support and those who attack "risk factor" epidemiology. This commentary aims to reinvigorate some of Geoffrey Rose's central arguments and show that this debate may miss a key point: a risk factor is a probabilistic concept that applies to an aggregate of individuals, not to a specific individual. Risk factor knowledge compels those in public health to seek actions that shift population distributions of these factors and, to do so, to understand their social, economic, and political determinants. The author links Rose's qualitative distinction between the causes of cases and the causes of incidence to an examination of the conceptual and quantitative limits of "individual risk" estimation. The attempt to predict individuals' futures on the basis of risk factor profile is especially prominent now with breast cancer. The author suggests reasons why a policy promoting private decision making about risk, while likely ineffective from a population standpoint, is viewed as the only feasible primary prevention option against this disease.