The birth of clinical epidemiology through the lens of Foucault’s typology of epistemes: what contribution to enlighten discussions on health economic evaluation?[La naissance de l’épidémiologie clinique au prisme de la typologie des épistémès de Foucault : quelle contribution pour éclairer les discussions actuelles sur l’évaluation économique en santé ?]

Background: Methods of health economic evaluation, also known as cost-effectiveness or cost-utility analyses, have been developed since the early 1980s. They are used in particular by health technology assessment agencies to guide public decision-making on the pricing and reimbursement of innovative and costly technologies (medicines, devices, public health programmes, etc.). These methods give rise to high expectations on the part of public institutions. They are indeed regarded as a means of improving information on the issues raised by the funding of costly interventions, and thereby of contributing to a greater democratisation of public decision-making. They are, however, subject to criticism from certain academic communities, much like the cost-benefit analysis methods to which they are akin (Adler and Posner, 1999). A first category of criticism concerns the incompleteness of the effects assessed due to the simplifying nature of the models used. A second category of criticism concerns the imperfections in methods for valuing health benefits (Le Pen, 2007 and 2009). It is common to attribute the criticism levelled at these economic evaluation methods to their multidisciplinary nature. These methods do indeed result from the convergence of two disciplines: welfare economics on the one hand and clinical epidemiology on the other. Objective: This article forms part of a research project aimed at utilising the methods and tools proposed by Michel Foucault to shed light on these discussions. The hypothesis explored here is that these two disciplines—welfare economics and clinical epidemiology—share a common epistemic framework, the modern episteme described by Foucault in his The Order of Things (1966), which is partly transgressed by economic evaluation in health. In this article, we examine more specifically the development of P-A Louis's ‘digital medicine' during the 19th century, which foreshadows contemporary clinical epidemiology and which we believe illustrates the transition from a classical episteme to a modern episteme. Method: To explore this hypothesis, we drew on the method of the archaeology of knowledge proposed by Foucault (1966, 1969). This involves studying various statements to identify both semantic and conceptual regularities and breaks, and thus comparing the ‘styles' of discourse. Unlike other approaches in the social sciences, the method of the archaeology of knowledge consists of analysing scientific discourses for their own sake, outside the social, economic and political context that gives rise to them. We began by establishing a corpus using an incremental research strategy (the ‘snowball' method). We then studied the various statements within this corpus. Result: The method employed allows us to distinguish between 18th-century discourses on ‘arithmetic medicine' and those developed by P-A Louis on the ‘numerical method'. What distinguishes them is neither the use of mathematics nor the comparative approach to assessing the effectiveness of treatments, but rather their conception of their ability to identify causal relationships concerning the onset of disease, its progression and the effectiveness of treatments. We then examine the practices that have developed within the framework of health economic evaluation regarding the modelling of chains of events and which appear to deviate from this theoretical framework.