Dennis Des Chene's Physiologia: Natural philosophy in late Aristotelian and Cartesian Though reconstructs the discourse of late scholastic natural philosophy, and assesses Descartes' agreements and disagreements. In a critical discussion, I offer a different interpretation of late scholastic theories of final causality and of God's concursus with created efficient causes. Fonseca's and Suárez' conceptions of final causality in nature depend on their claim that a single action can be the action can be the action of two agents at once-in particular, of God and of a creature. I discuss both their teory of action and its implications for natural teleology. I then compare Descartes, emphasizing his demolition of the Aristotelian hierarchy of causes, with unmoved movers(culminating in God) regulating the action of inferior moved movers. Aristotle argues that unmoved causes are needed to produce a stable world-order; be takes arts(Texval) as his models of unmoved causes, and uses this model to suport natural teleology. Descartes radically simplifies this system by denying all unmoved movers other than God, and denying anything analogous to an art in non-human nature. I explore the implications for Descartes'notion of concursus and his criticism of natural teleology, and discuss his resulting difficulties in explaining natural stability.