CONCEPT
The Free Energy Principle
Karl Friston’s claim that any system persisting as a distinct entity in a changing world must minimize the divergence between its internal model and its sensory evidence—a thermodynamic necessity that, when generalized, derives perception, action, curiosity, and the self from a single mathematical principle.
The free energy principle begins where most theories of mind do not: not with what brains do, but with what anything must do simply to persist as a separate thing in a world tending toward disorder.
Karl Friston’s answer, developed across four decades of work at University College London, is that any self-organizing system must minimize a quantity he calls free energy—formally, a variational bound on the surprise that the system’s sensory data represents given its internal model. A cell maintains its chemistry within viable bounds; a brain maintains its beliefs within the bounds of its generative model; an organism maintains its physiological states within the bounds compatible with life. All three are, in Friston’s vocabulary, minimizing free energy. The principle unifies perception (updating the model to fit the data) and
action (changing the world to fit the model) under a single variational framework, and derives from this unification a