Causalité et pensée médicale : un cas en controverse

Abstract

Questions of method in medicine are always posed in situations that are empirically difficult. The etiological model, undoubtedly still the dominant model in medicine, including in psychiatry, finds its justifications in the method, which proceeds from causality. The author recalls the history of the concept of causality, which, from the time of the Aristotelian and Arabic traditions (astrology and mathematics), was founded on the idea of a necessary order of the world, an order in which all events are linked. This conception was taken up by Renaissance philosophers and integrated into the epistemology of modern sciences since Copernicus, Kepler and Galileo, along with some notions of neoplatonic and medieval schools, that is, that of order and first cause. In the history of philosophy, it may be acknowledged that two traditions distinguish themselves on these questions: that of the rationalist and analytic tradition (according to the terms used by Descartes), and the empirical tradition. The rationalist principle becomes, with the Romantic movement, the inspiration for a priori and idealist doctrines; leading the way in medicine are Laplace and Claude Bernard. The empirical current of causality found its bases in the philosophy of Al Ghazali in the 11th century. However, it is to Hume that we owe a theory of causality that excludes an a priori deductibility of things and affirms the method of the proof of the link. Contemporary scientific epistemology is dominated by a neo-Humean conception of causality. The empirical method of causality significantly influenced the evolution of medicine and neurological and psychiatric conceptions of the brain. Suffice it to evoke, among others, pioneers such as Gall, and also Broca and Wernicke. The author articulates these historical considerations with neurological and psychological clinical data of a particular case. A controversial case, Parkinson's disease, illustrates the limits of the causality method in clinical practice. The author shows the value of considering the contradiction between the interpretation of clinical signs and technical investigations and the diagnostic certainly represented by an autopsy. The latter permits the establishment of a linear explanation of cause and effect, that is, a precise lesion corresponding to a known disease. The etiological model is thus confirmed thanks to the autopsy model; hence the need to reconsider clinical practice, its epistemology, and the validity of causal reasoning. We may observe that the debate between “topographical” and “functional” diagnoses arises, doubtless, from an old medical quarrel, which remains open despite the present finesse of tools at our disposal. We would be permitted to think that, without agreement between “topographical” and “functional” diagnoses, the interpretation of data should make these two fields interact in some other way. The author supports her argument by a phenomenological and psychoanalytical approach and identifies a clinical humanist episteme founded on indeterminism and which therefore takes into account that the observer and the observed define a field of experience that is limited and relative, always subject to double inference. The epistemological proposition, which follows, suggests leaving behind reasoning according to diagnostic categories and rather basing clinical practice on the understanding of the “course of the particular case through the disease”. The categorical method in medicine could give way to the more qualitative concept of the patient's experience and of his condition of being-in-the-world in its intersubjectivity. This would lead the clinician to leave behind etiology in favour of quantum, that is, probabilist, causality.