This paper outlines seven essential characteristics of medical evidence and describes the implications of these for both the theory of evidence-based medicine and clinical practice. The seven characteristics are: (1) Provisional; (2) Defeasible; (3) Emergent; (4) Incomplete; (5) Constrained; (6) Collective and (7) Asymmetric. It is argued that the epistemological theory that best fits medical evidence is that of fallibilism.