Problems with using mechanisms to solve the problem of extrapolation

Jeremy Howick*, Paul Glasziou, Jeffrey K. Aronson

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

54 Citations (Scopus)


Proponents of evidence-based medicine and some philosophers of science seem to agree that knowledge of mechanisms can help solve the problem of applying results of controlled studies to target populations ('the problem of extrapolation'). We describe the problem of extrapolation, characterize mechanisms, and outline how mechanistic knowledge might be used to solve the problem. Our main thesis is that there are four often overlooked problems with using mechanistic knowledge to solve the problem of extrapolation. First, our understanding of mechanisms is often (and arguably, likely to remain) incomplete. Secondly, knowledge of mechanisms is not always applicable outside the tightly controlled laboratory conditions in which it is gained. Thirdly, mechanisms can behave paradoxically. Fourthly, as Daniel Steel points out, using mechanistic knowledge faces the problem of the 'extrapolator's circle'. At the same time, when the problems with mechanistic knowledge have been addressed, such knowledge can and should be used to mitigate (nothing can entirely solve) the problem of extrapolation.

Original languageEnglish
Pages (from-to)275-291
Number of pages17
JournalTheoretical Medicine and Bioethics
Issue number4
Publication statusPublished - Aug 2013


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