This essay focuses on the structure of agency in Georg Ernst Stahl's model of organic order and the role that it plays for the difference between living and non-living beings in the discourses of medicine and natural history around 1700. Stahl calls the order of organic beings an "organism". He characterizes the "organism" through the notions of tonic movement, energy and ratio. The tonic movement is a mechanism of contraction and relaxation of organic units to direct fluids to certain parts of the body; the energy represents a certain, limited potential of the living body to act spontaneously and to react if it is irritated; and the ratio expresses the logic of a processual, directed order imposed on corporeal dispositions. This ratio inheres in natural agents. However, to establish his theory of agency, Stahl first analyzes the irregular blood movements that characterize diseases. The capacity of the organic body to change these movements and to heal itself in redirecting them, leads him to the assumption that such bodies can regulate their own order and that self-regulation requires an autonomous agent.