Freud’s version of free energy (he used the same term) was similar to his notion of excitation: an uncomfortably stimulating psychic energy, which the nervous system sought to discharge. “Accumulation of excitement,” he wrote in “The Interpretation of Dreams,” “is perceived as pain and . . . the diminution of the excitement is perceived as pleasure.” The urge to discharge the free energy was what drove a person to act—to move around, to seek sex, to work. Friston’s version of free energy—prediction error—could sound at first as if it were all about cognition, just as Freud’s version could sound at first as if it were all about sex, but at root they were both about survival. Minimizing prediction error, in other words, was much bigger than it sounded. When the brain strove to minimize prediction error, it was not just trying to reduce its uncertainty about what was going on in the world; it was struggling to resolve the contradictions between fantasy and reality—ideally by making reality more like fantasy. The brain had to do two things in order to survive: it had to impel its body to get what it needed, and it had to form an understanding of the world that was realistic enough to guide it in doing so. Free energy was the force that drove both. – The mind expanding ideas of Andy Clark, Larissa MacFarquhar (The New Yorker, 2018)