Theory Based Medicine and the Role of Evidence: Why the Emperor Needs New Clothes, Again

The evidence based medicine movement ("EBM") was established to combat capricious reasoning in clinical care, particularly arguments from authority. Critique of authority and appraisal of evidence remain EBM's core values, and should be revisited in this current era of EBM's maturity and considerable influence. At this stage, we encounter a new form of under-questioned authority: evidence from well-designed and methodically appraised RCTs. RCT evidence is now prized even on some occasions when it is incapable of providing meaningful information - in particular, when underlying casual theory is inscrutable. This is the case with many health interventions whose mechanisms remain "black boxes" without compelling explanations. A review of recent clinical trials of remote intercessory prayer illustrates this problem. The findings of these trials are uninterpretable and inapplicable, due to unresolved and fundamental theoretical problems with their hypotheses and premises. Yet this trial evidence has gained remarkable scientific credibility and high profile dissemination, largely on the warrant of rigorous RCT methodology. The case of remote intercessory prayer evidence helps to identify some systematic blind spots in the institutions of EBM. As EBM has long counselled, clinicians and policy makers should indeed be sceptical of casual arguments in the absence of empirical evidence. However, empirical evidence in the absence of good casual argument is likewise occasion for scepticism. Medicine - even evidence-based medicine - is theory-based at its core. EBM must cultivate greater capacity to address the crucial role of theory, in both the generation and the use of experimental evidence.