“This is absolutely novel in history,” Ramstead told me as we sat on a bench in Queen Square, surrounded by patients and staff from the surrounding hospitals. Before Friston came along, “We were kind of condemned to forever wander in this multidisciplinary space without a common currency,” he continued. “The free energy principle gives you that currency.”

In 2017, Ramstead and Friston coauthored a paper, with Paul Badcock of the University of Melbourne, in which they described all life in terms of Markov blankets. Just as a cell is a Markov-blanketed system that minimizes free energy in order to exist, so are tribes and religions and species.

After the publication of Ramstead’s paper, Micah Allen, a cognitive neuroscientist then at the FIL, wrote that the free energy principle had evolved into a real-life version of Isaac Asimov’s psychohistory,11 a fictional system that reduced all of psychology, history, and physics down to a statistical science.

11 In Foundation, published in 1951, one of Asimov’s characters defines psychohistory as “that branch of mathematics which deals with the reactions of human conglomerates to fixed social and economic stimuli.”

And it’s true that the free energy principle does seem to have expanded to the point of being, if not a theory of everything, then nearly so. (Friston told me that cancer and tumors might be instances of false inference, when cells become deluded.) As Allen asked: Does a theory that explains everything run the risk of explaining nothing?

On the last day of my trip, I visited Friston in the town of Rickmansworth, where he lives in a house filled with taxidermied animals12 that his wife prepares as a hobby.

12 On a recent Saturday, a man came to the door asking if Friston’s wife was home. When Friston said yes, the man said, “Good, because I got a dead cat here.” He wanted it stuffed.

As it happens, Rickmansworth appears on the first page of The Hitchhiker’s Guide to the Galaxy; it’s the town where “a girl sitting on her own in a small café” suddenly discovers the secret to making the world “a good and happy place.” But fate intervenes. “Before she could get to a phone to tell anyone about it, a terrible stupid catastrophe occurred, and the idea was lost forever.”

It’s unclear whether the free energy principle is the secret to making the world a good and happy place, as some of its believers almost seem to think it might be. Friston himself tended to take a more measured tone as our talks went on, suggesting only that active inference and its corollaries were quite promising. Several times he conceded that he might just be “talking rubbish.” During the last group meeting I attended at the FIL, he told those in attendance that the free energy principle is an “as if” concept—it does not require that biological things minimize free energy in order to exist; it is merely sufficient as an explanation for biotic self-organization.

Friston’s mother died a few years ago, but lately he has been thinking back to her frequent reassurances during his childhood: You’re very intelligent, Karl. “I never quite believed her,” he says. “And yet now I have found myself suddenly being seduced by her argument. Now I do believe I’m actually quite bright.” But this newfound self-esteem, he says, has also led him to examine his own egocentricity.

Friston says his work has two primary motivations. Sure, it would be nice to see the free energy principle lead to true artificial consciousness someday, he says, but that’s not one of his top priorities. Rather, his first big desire is to advance schizophrenia research, to help repair the brains of patients like the ones he knew at the old asylum. And his second main motivation, he says, is “much more selfish.” It goes back to that evening in his bedroom, as a teenager, looking at the cherry blossoms, wondering, “Can I sort it all out in the simplest way possible?”

“And that is a very self-indulgent thing. It has no altruistic clinical compassion behind it. It is just the selfish desire to try and understand things as completely and as rigorously and as simply as possible,” he says. “I often reflect on the jokes that people make about me—sometimes maliciously, sometimes very amusingly—that I can’t communicate. And I think: I didn’t write it for you. I wrote it for me.”

Friston told me he occasionally misses the last train home to Rickmansworth, lost in one of those problems that he drills into for weeks. So he’ll sleep in his office, curled on the futon under his Markov blanket, safe and securely separated from the external world.

Shaun Raviv (@ShaunRaviv) is a writer living in Atlanta, Georgia.

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