Evidence of mechanism in the evaluation of streptomycin and thalidomide.

This paper considers what evidence is needed to establish the effectiveness and safety of a drug therapy. The claim that A cures D is a particular case of a causal claim in medicine. So the paper begins with a general analysis of the evidence for causal claims in medicine. Such evidence is divided into two types: statistical evidence and evidence of mechanism. These are further divided into observational and interventional, producing a 2x2 classification. It is shown that historically there have different assessments of the importance of these different types of evidence. Evidence-based medicine (EBM) puts forward the thesis that claims of the form 'A cures D without harming the patient' can be established using only randomized controlled trials or RCTs. This thesis of EBM is criticized by considering two historical examples: streptomycin and thalidomide. Generalizing from these, it is claimed that the effectiveness and safety of a drug therapy can only be established by using both statistical evidence and evidence of mechanism. This is a specific instance of the Russo-Williamson thesis.

The evidence that evidence-based medicine omits.

According to current hierarchies of evidence for EBM, evidence of correlation (e.g., from RCTs) is always more important than evidence of mechanisms when evaluating and establishing causal claims. We argue that evidence of mechanisms needs to be treated alongside evidence of correlation. This is for three reasons. First, correlation is always a fallible indicator of causation, subject in particular to the problem of confounding; evidence of mechanisms can in some cases be more important than evidence of correlation when assessing a causal claim. Second, evidence of mechanisms is often required in order to obtain evidence of correlation (for example, in order to set up and evaluate RCTs). Third, evidence of mechanisms is often required in order to generalise and apply causal claims. While the EBM movement has been enormously successful in making explicit and critically examining one aspect of our evidential practice, i.e., evidence of correlation, we wish to extend this line of work to make explicit and critically examine a second aspect of our evidential practices: evidence of mechanisms.

Hempelian and Kuhnian approaches in the philosophy of medicine: the Semmelweis case.

Semmelweis's investigations of puerperal fever are some of the most interesting in the history of medicine. This paper considers analysis of the Semmelweis case. It argues that this analysis is inadequate and needs to be supplemented by some Kuhnian ideas. Kuhn's notion of paradigm needs to be modified to apply to medicine in order to take account of the classification schemes involved in medical theorising. However with a suitable modification it provides an explanation of Semmelweis's failure which is argued to be superior to some of the external reasons often given. Despite this success in applying Kuhn's ideas to medicine, it is argued that these ideas must be further modified to take account of the fact that medicine is not a natural science but primarily a practice designed to prevent and cure diseases.