The outcomes movement--including evidence-based medicine--challenges medicine as a profession by disputing what and how physicians know. First, the movement considers probabilistic research to be virtually the only way to arrive at knowledge in medicine. Second, it insists on objective or impersonal knowledge (statistically manipulated, hard, aggregate data). Such knowledge does not come from within the professional relationship; rather it is gathered across relationships and is offered to the practitioner from the outside. Third, the outcomes movement is motivated by a desire for certainty, promising definitive solutions that will reduce variation and waste. What professionals know, in contrast, is inherently and irreparably uncertain. Fourth, the movement expects physicians to implement the findings from probabilistic research through application. The inferential leap necessary for treating an individual based on aggregate findings is mostly assumed away. Finally, the outcomes movement promotes rule-based behavior on the part of physicians in an effort, among other things, to eliminate variation in medical practice. But professionals do not follow rules per se--they intuit what is right in a situation, including, sometimes, that it is right to defer to a rule. Professional knowledge in medicine is both larger and smaller than the knowledge conceived of by the outcomes movement. The latter is built of probabilistic research and translated into physician directives. Professional knowledge, in contrast, partakes of statistical knowledge and bench science, as well as various forms of personal knowledge, including the experiential. Physicians will continue to need professional knowledge, which allows for the complexity of physician experience and for the immediacy and individuality of patients.