Who Is Thinking?

A World Appears: A Journey into Consciousness by Michael Pollan; Penguin Press, 320 pp., $32

In 1998, philosopher David Chalmers made a bet with neuroscientist Christof Koch about whether, in the next 25 years, any scientist would be able to offer a persuasive and precise explanation for how our messy, spongy brains give rise to the feeling of awareness. Koch wagered that the puzzle could be solved. Four years earlier, Chalmers was a somewhat disheveled postdoctoral fellow at Washington University in St. Louis. He sent an abstract to the first Science of Consciousness meeting, hoping simply to present his research on a conference poster. Instead, he found himself on the main stage, where he delivered a characterization of the problem of studying consciousness that, even today, remains central to the field—namely, that there are many relatively easy problems to solve (how things like perception, cognition, and decision-making work, neuroscientifically), and one “hard problem”: determining why any of those electrical, neural, and molecular stories should lead to what it feels like to be you.

In his new book, A World Appears: A Journey into Consciousness, Michael Pollan walks us through the current state of the debate. Pollan is one of our finest science writers and, to judge by this book, a lovely person with deep curiosities and patience and openness. He tells us that he backed into the topic slowly and unexpectedly. He recalls how he once took a dose of magic mushrooms, sat in his garden, and felt that his plants were talking to him. He couldn’t get the experience out of his mind, and now, after literary forays into what exactly was going on with those mushrooms (How to Change Your Mind, This Is Your Mind on Plants), he has turned his attention to the grand, deep puzzle of how to make sense of consciousness itself.

What follows is a series of curated Platonic dialogues, with Pollan playing Socrates, the wise fool, posing questions to current experts until they both come to the limits of their understanding. First there is the puzzle of what it means to be sentient. Philosopher Paco Calvo and plant neurobiologist Stefano Mancuso insist that plant roots make choices, recognize opportunities, solve problems. “I had always assumed,” Pollan writes, “that bean plants simply grow this way or that until, by pure chance, they bump into something to climb.” Calvo tells Pollan that when one lengthens the time scale of observation, plants seem more intentional. Mancuso even thinks that plants sleep.

Then Michael Levin, a developmental biologist at Tufts, uses bioelectric networks to broaden the definition of sentience. Levin creates “Xenobots,” multicellular organisms not seen in nature, by scraping cells together in a way that allows a new bioelectrical field to emerge. Cells meant to be the skin of tadpoles become something else, and as they do that, they appear to have a kind of intentional, purposive quality. At this point, we are well past plants. “I see an incredibly mindful world,” Levin tells Pollan.

Then there are the neuroscientific theorists, like Karl Friston of University College London, who “is responsible for many of the computational tools used to interpret brain imaging.” Friston places inference at the center of his theories. His basic question is how any complex system—from viruses to ecosystems—survives in the face of entropy. Such systems must have a boundary, a sensory apparatus, and some ability to act. The system has to figure out what to do, and then do it. And again, everything now seems at least close to conscious. “Sentience,” Pollan writes, “or something like it—the ability to sense, to infer, to predict—reaches all the way down to the very simplest creatures and emerges when life does, if not before.”

Sentience is not quite consciousness, but at this level, it becomes harder to tease apart what makes consciousness special. Pollan seems at once most persuaded and most unnerved by cognitive neuroscientist Anil Seth, who has taken predictive processing, a newly chic theory about the brain, as far as it can go. Predictive processing theories start from the premise that our brains are prediction machines that have evolved to help us to survive. From this perspective, we do not see the world as it is; we see the world as our perceptual apparatus predicts it should be in order to allow us to maneuver within it. All that we experience is based on expectation, constantly corrected and developed, but expectation nonetheless. Seth goes so far as to call perception a “controlled hallucination.” Our awareness of being a self, he asserts, is a controlled hallucination, too. “I found this hard to believe,” Pollan writes, and he then proceeds to make sense of it.

Consciousness is a tough topic. There is a kind of boys-with-big-machines vibe to some of this material, and it is hard not to feel skeptical about how much these theories really explain. What I find moving in these discussions is the intense yearning for a world that is more alive than secular scientists might think it is, a kind of seeking for a god that one suspects these scientists do not, at the same time, believe to exist. It is hard not to notice, at consciousness conferences, the mixture of science and seeking, of seeking scientists and science-minded seekers, wanting what the church would give them but determined not to step inside its doors. It is no accident that interest in this new science of consciousness has exploded as participation in mainstream religion has plummeted. For Pollan, despite his fascination with the science of consciousness, the science itself is not enough. He concludes his book with poetry, with the American Zen Buddhist teacher Joan Halifax in Santa Fe, and with solitary meditation in a cave. You get the sense that for all of them, the satisfaction is in the search.

David Chalmers won his wager with Christof Koch. In June 2023, Nature carried a picture of the two of them shaking hands at the annual meeting of the Association for the Scientific Study of Consciousness in New York City, where Koch then handed Chalmers a case of fine Madeira. Both men seemed chipper. They’ve renewed the bet for another 25 years.

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