Between chemistry and biology : nutrition, organization, identity ; Entre chimie et biologie : nutrition, organisation, identité

It is possible to isolate, among the attempts to define living organisms, two competing traditions: one has made reproduction the proper of living organisms, while the other has seen in nutrition and then metabolism (the material process by which an organism maintains itself by transforming a foreign matter into a living substance) an essential property and a criterion for the unification of ail living forms. However, the second term of this polarity is in tum subdivided into a pem1anent movement of oppositions that seems to characterize life as an incessant "whirlwind", an uninterrupted circulation or constant flow of matter between the inside and the outside, the bodies and their environment. This work is devoted to exploring the conceptual changes within this second tradition, nutrition and metabolism. How did metabolism become a problem for biology? This thesis proposes a genealogical analysis of the concept of metabolism understood both as a bridge linking the vital specificity of organisms to their chemical conditions of existence, and as a scheme through which self-production and the maintenance of biological identity could be approached from a naturalistic perspective. This thesis proposes a history of the developments of a material, chemical and life theory and shows, in the same movement, how the elaboration of an "epistemic space" around the concept of metabolism has gradually made it possible to redefine the contours under which the question of biological identity has since been addressed. ; Il est possible d'isoler, parmi les tentatives de définition du vivant, deux traditions concurrentes : l'une a fait de la reproduction le propre du vivant, tandis que l'autre a vu dans la nutrition puis le métabolisme (le processus matériel par lequel un organisme se maintient en transformant une matière étrangère en substance vivante) une propriété essentielle et un critère d'unification de toutes les formes vivantes. Or, le second terme de cette polarité se subdivise à son tour en un mouvement permanent ...