Placebo-Controlled Trials and the Logic of Clinical Purpose

The exercise of human intelligence ramifies in numerous and diverse ways. Nevertheless, as applied in theory or practice, in work or play, directed toward life or toward death, each manifestation shares a common underlying method: organized comparison. Whether deriving equations in mathematics, or developing progressions of chords in jazz, or, in business, studying the impact of advertisements upon defined populations, reason is at bottom engaged in the single process of comparison, the delineation of sameness and difference. Medicine partakes of this commonality of method, and has come to grant greatest credence to those propositions established by the cleanest possible comparison: the controlled clinical trial that methodically examines sameness and difference in outcome across cohorts. All of the diverse strategies introduced to reduce bias (e.g., stratification and randomization) in fact simply aim to ensure the precision of comparison. In pursuing the strategy of organized comparison, however, a prior question must be posed: For what purpose is comparison sought? Many of the controversies concerning the design of clinical trials can be best understood as