There is a rather obvious “ecological” presupposition lurking behind medical treatment, one that we no longer take seriously when we become fascinated both with the objectifying capacities of the sciences and with the naturalizing philosophical projects that rely upon these capacities. Drawing upon Georges Canguilhem and clinical phenomenology, this article underlines the deep semantic ambiguity of concepts such as health and illness in order to show their legitimate field of application and how these terms are not immune to relations of power that are intrinsic to every social existence.