On evidence and evidence-based medicine: Lessons from the philosophy of science

Abstract

The evidence-based medicine (EBM) movement is touted as a new paradigm in medical education and practice, a description that carries with it an enthusiasm for science that has not been seen since logical positivism flourished (circa 1920–1950). At the same time, the term “evidence-based medicine” has a ring of obviousness to it, as few physicians, one suspects, would claim that they do not attempt to base their clinical decision-making on available evidence. However, the apparent obviousness of EBM can and should be challenged on the grounds of how ‘evidence’ has been problematised in the philosophy of science. EBM enthusiasm, it follows, ought to be tempered.

The post-positivist, feminist, and phenomenological philosophies of science that are examined in this paper contest the seemingly unproblematic nature of evidence that underlies EBM by emphasizing different features of the social nature of science. The appeal to the authority of evidence that characterizes evidence-based practices does not increase objectivity but rather obscures the subjective elements that inescapably enter all forms of human inquiry. The seeming common sense of EBM only occurs because of its assumed removal from the social context of medical practice. In the current age where the institutional power of medicine is suspect, a model that represents biomedicine as politically disinterested or merely scientific should give pause.

Introduction

To have evidence is to have some conceptual warrant for belief or action (Goodman 2003, p. 2), and it is the practice of basing all beliefs and practices strictly on evidence that allegedly separates science from other activities (Husserl, 1982; Kuhn, 1996). The evidence-based medicine (EBM) movement purports to eschew unsystematic and “intuitive” methods of individual clinical practice in favour of a more scientifically rigorous approach. This rigour is achieved through methodological clinical decision-making based on examination of evidence derived from the latest clinical research. Evidence as accumulated data has been made widely and easily available to clinicians and educators by evolving information technologies, and EBM aficionados, such as those found in the Cochrane Collaboration (Grimshaw, 2004) and on the editorial boards of various evidence-based practice journals, describe the movement as a new paradigm in medical education and practice, a description that carries with it a science enthusiasm that has not been seen since the days of positivism.

The term “evidence-based medicine”, and its standard definition as “the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients” (Sackett, Rosenberg, Gray, Haynes, & Richardson, 1996, p. 71), has a ring of obviousness to it which makes it difficult to argue against. Few doctors, one suspects, would be willing to assert that they do not attempt to base their clinical decision-making on available evidence.¹ However, the apparent obviousness of EBM can and should be challenged on the grounds of how ‘evidence’ has been problematised in the philosophy of science. In this paper, I argue that evidence-based practices maintain an antiquated understanding of evidence as “facts” about the world in the assumption that scientific beliefs stand or fall in light of the evidence. This understanding of evidence is explicitly positivist, and such a picture of science has been seriously undermined by post-positive philosophies of science. EBM's ability to guide healthcare decision-making by appealing to “the evidence” as the bottom line is attractive to many because it proposes to rationalise this complex social process. Yet it does so through the positivistic elimination of culture, contexts, and the subjects of knowledge production from consideration, a move that permits the use of evidence as a political instrument where power interests can be obscured by seemingly neutral technical resolve.

Logical positivism is a philosophical system that recognises only scientifically verifiable propositions as meaningful. This school of thought originated in Vienna in the 1920s by a group of philosophers and scientists concerned with the philosophy of formal and physical science. However, it was their attitude toward science and its relationship to philosophy that defines the “Vienna Circle”. Because the Circle rejected the possibility of justifying knowledge claims that were “beyond” the scope of science, they dismissed metaphysics and many of the claims made in theology and ethics as nonsensical (or unverifiable). Emigration by many of the Circle's members to Britain and the United States during the early war years led to the strong influence of logical positivism on Anglo-American analytic philosophy. The “post-positive turn” in the philosophy of science refers to the critical examinations of scientific thought and practice that originated in the second half of the 20th century by such historically oriented philosophers as Thomas Kuhn, Norwood Hanson, and Paul Feyerabend. Their historical analyses of scientific change and progress undermined the positivist–empiricist endorsement of the claims of science to provide a value-free understanding of the natural world. Their examination of the relationship between science and values (and the denial of their possible or even preferable separation) has been enriched by the insights of feminist epistemologies of science and phenomenological investigations. Feminist epistemologists have exposed the political stakes in knowledge production by demonstrating the androcentric assumptions underlying conventional understandings of scientific thought and practice, while phenomenologists have questioned the goals and methods of scientific medicine through examination of the patient's lived experience of illness and dis-ease. In this paper, I take the lessons learned from post-positivist, feminist, and phenomenological epistemologies of science's critiques of the presumed “self-apparentness” of evidence and consider their implications for EBM.