[Draft manuscript of a forthcoming MIT Press monograph.] The Free Energy Principle proposes to reduce the goal-directed behaviour of a living agent to the preservation of homeostasis and then to analyse cognition as the process of pursuing this goal. I argue that this stability-based account fails to capture the two features that distinguish the intentional actions of biological agents from the mere movements of inanimate machines: namely 1) the precarious dependence of their bodily structure upon the very metabolic processes that it supports and 2) their potential for developmental changes in this structure. It is only by rejecting the presumption of a machine-style separation between structure and processes that we can capture this uniquely precarious status of living systems, in virtue of which they may be described as autonomous agents, acting towards the goal of their own continued survival.