A premise which seems to be preponderate in the philosophy of medical practice developed by Pellegrino and Thomasma is the medical prescription to save life whenever possible. This premise is confronted with a polemical vitalism and examined in the light of some reading principles derived from G. Canguilhem's philosophy of the life-sciences. It is argued that the primarity of life in the account given by Pellegrino and Thomasma of the foundations of medical practice is closely related to biological concepts of life. This relation is shown to be problematic. The biological concept results in an ontology of the living body as the condition of possibility of medical practice, thus linking up this practice with an uncriticized biological value and finality.