Abstract
Even though the evidence‐based medicine movement (EBM) labels
mechanisms a low quality form of evidence, consideration of the mechanisms on
which medicine relies, and the distinct roles that mechanisms might play in clinical
practice, offers a number of insights into EBM itself. In this paper, I examine the
connections between EBM and mechanisms from several angles. I diagnose what
went wrong in two examples where mechanistic reasoning failed to generate
accurate predictions for how a dysfunctional mechanism would respond to
intervention. I then use these examples to explain why we should expect this kind of
mechanistic reasoning to fail in systematic ways, by situating these failures in terms
of evolved complexity of the causal system(s) in question. I argue that there is still a
different role in which mechanisms continue to figure as evidence in EBM: namely,
in guiding the application of population‐level recommendations to individual
patients. Thus, even though the evidence‐based movement rejects one role in which
mechanistic reasoning serves as evidence, there are other evidentiary roles for
mechanistic reasoning. This renders plausible the claims of some critics of evidencebased
medicine who point to the ineliminable role of clinical experience. Clearly
specifying the ways in which mechanisms and mechanistic reasoning can be
involved in clinical practice frames the discussion about EBM and clinical experience
in more fruitful terms.