The Free-Energy Principle: A Unified Brain Theory?

The paper articulating the free energy principle — the argument that all biological systems, from single cells to complex brains, act to minimise surprise (or equivalently, free energy) by updating their internal models of the world or acting on the world to confirm their predictions. Friston's framework unifies perception, action, and learning under a single variational principle borrowed from statistical physics. The writing is notoriously difficult, but the core idea has become the most ambitious attempt at a unified theory of brain function in contemporary neuroscience. An obligatory reference for understanding predictive processing and its implications for how organisms — and by extension, users — navigate uncertainty.