Avis de soutenance - doctorat - Laurence TERZAN

This thesis explores microbiotic symbiosis and its far-reaching implications across medicine, biology, philosophy, epistemology,, and ethics. By confronting the classical definition of symbiosis with contemporary developments in both biology and philosophy, it seeks to rethink its very meaning. In conceiving the living organism as a holobiont, an entity constituted through perpetual relations, microbiotic symbiosis introduces a profound ontological and semantic shift. This conceptual refoundation is then placed in dialogue with its extension to the human sciences, in order to examine, and ultimately ground, its legitimacy. From this perspective, fundamental philosophical notions such as identity, the ontology of the living, and causality can no longer be grasped within their traditional frameworks. The individual appears no longer as a self-contained unity, but as a plurality; its being is not fixed, but unfolds as a dynamic process, continuously negotiated and co-constructed. The thesis then turns to medicine, showing how a discipline long structured by a logic of opposition, of fighting disease, can no longer overlook the central role of microbiotic symbiosis. The concepts of disease and therapy are revisited in light of this new understanding, giving rise to deeper questions concerning causality and the very nature of illness. The question «Why disease?» thus emerges as the guiding thread of this inquiry, grounded in a biological and epistemological analysis of evolution that we describe as «symbio-epigenetic.».