Introduction Evidence-based medicine (EBM) is defined as ‘the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients’ (Sackett et al. 1996). Despite the success of the dissemination of the concept of ‘evi- dence-based health care’ there are several aspects of the movement that remain problematic. Critics have argued that evidence-based approaches represent a narrow reductionism that ignores clinical judgement and experience and that evidence-based approaches foster an inappropriate reliance on epidemiology and statistical methodology, particularly a dogmatic adherence to the randomized control trial (RCT) (Miles et al. 1997, 1998, 1999, 2000, 2001; Charlton 1997;Tonelli 1998). Others argue that evidence-based approaches neglect the true underlying issue that relates to what and how physicians and health care workers know (Tanenbaum 1993; Malterud 1995).That empirical studies have not shown conclusively the superiority of evidence-based approaches is regarded as an important and telling fault for a theory based on the primacy of research evidence (Norman 1999). These perceptions may stem from a legitimate concern over what counts as evidence in the first place. (Feinstein & Horwitz 1997, Miettinen 1998) The priority given to the application of research- based evidence over clinical knowledge in practice, and the limitation of what constitutes evidence in the current evidence-based paradigm to what can be ex- pressed as a probability are two additional problems (Miller & Safer 1993, Upshur 1999). Furthermore, in early conceptions of evidence-based medicine, values are conceived either in opposition to evidence or are relegated to footnote considerations. However, it is clear that at each level of decision- making, values are regarded as crucial components of appropriate health care. The existence of large grey zones in clinical practice underscores the impor- tance of eliciting and respecting patient values and openly acknowledging uncertainty. (Naylor 1995) As Pelligrino has noted, evidence enters any discourse in health care as a means of testing assertions and providing support for arguments.As there is a dimen- sion of persuasion inherent in the use of evidence, it has an inescapable moral dimension. Therefore, Pelligrino recognizes the need to develop a theory of evidence that inquires into the existence, nature and kinds of evidence that exist (Pelligrino 1999). The tension between values and evidence points out a neglected aspect of the EBM debate. The Journal of Evaluation in Clinical Practice, 8, 2, 113–119 © 2002 Blackwell Science 113 Correspondence Dr Ross E.G. Upshur Joint Centre for Bioethics University of Toronto 2075 Bayview Avenue – Room E349B Toronto, Ontario Canada M4N 3M5 E-mail: rupshur@idirect.com Keywords: evidence-based medicine, medical epistemology, medical reasoning Accepted for publication: 8 February 2002 If not evidence, then what? Or does medicine really need a base? Ross E. G. Upshur BA(Hons) MA MD MSc FRCPC Director, Primary Care Research Unit, Sunnybrook and Women’s College Health Sciences Centre, and Assistant Professor, Departments of Family and Community Medicine and Public Health Sciences and Joint Centre for Bioethics, University of Toronto, Toronto, Ontario, Canada Abstract This essay analyses the concept of ‘base’ in relation to its use in evidence- based medicine (EBM). It evaluates the extent to which evidence provides a sufficient base for health care to rest and discusses whether medicine needs a base, and, if so, what are the other possible candidates. This paper will argue that EBM is linked epistemologically to the theory of foundationalism and shows how important criticisms of EBM emerge from anti-foundationalist epistemologies and interpretive frameworks. Drawing from recent writings in the philosophy of science, it is argued that there is a need to see multiple perspectives relevant to the practice and understanding of medicine.