For years now, Hakwan Lau has suffered from an inner torment. Lau is a neuroscientist who studies the sense of awareness that all of us experience during our every waking moment. How this awareness arises from ordinary matter is an ancient mystery. Several scientific theories purport to explain it, and Lau feels that one of them, called integrated information theory (IIT), has received a disproportionate amount of media attention. He’s annoyed that its proponents tout it as the dominant theory in the press. He’s disturbed by their apparent affinity with New Age figures, such as Deepak Chopra. Worst of all, he complains, the theory doesn’t even rise to the level of “science.”

IIT was first formulated by Giulio Tononi in 2004. It’s meant to quantify the consciousness that exists in any system, based on the total information that is brought together by its constituent parts. Other theories of consciousness tell more of a general story about how the brain generates consciousness; IIT gives it a mathematical expression. Controversially, IIT also suggests that there is consciousness in systems that we wouldn’t usually think of as being aware, including photodiodes and thermostats. Anil Seth, a neuroscientist who is not himself opposed to IIT, nonetheless described it to me as “kind of a bonkers theory.”

Lau has expressed his many concerns to colleagues at conferences, in the hallways between sessions and afterward over drinks at the bar. Many of them have been sympathetic, he told me, and share his fear that their whole field would be a laughingstock if a theory that deems smoke alarms conscious were to be taken as its public face. Lau also worries that naive students could be deluded into thinking that the theory is stronger—or perhaps less bonkers—than it really is. This summer, Lau set about convincing his colleagues that they should express their contempt for IIT as a group, in print. He succeeded: On September 16, more than 100 of them released an open letter. Within 24 hours, a full-blown brawl had broken out on social media.

Scientists who study consciousness are touchy about the way the field is perceived. They’ve been fighting for respectability for decades. “It wasn’t always treated as a particularly legitimate thing to do,” Seth told me. The field has been largely isolated from mainstream psychology and neuroscience, and as a result, researchers can have trouble attracting funding. Consciousness research has gradually become more accepted, but even today it’s not often bankrolled by the National Science Foundation or the National Institutes of Health. Many scientists must instead rely on private donors.

In 2020, a consortium of scientists and philosophers secured $3.2 million from one such donor, the Templeton World Charity Foundation, for a series of “adversarial” experiments. The idea was for proponents of different theories of consciousness to design experiments using neuroimaging technology, and to agree, in advance, which results would support which theory. In June of this year, they announced the first results from a showdown that pitted IIT against the theory that consciousness arises from something called a “workspace” that brings together information from the senses and other cognitive processes into a coherent whole and broadcasts it to other neural regions. The outcome was largely unsatisfying.

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Existing technology is still too crude to test either theory’s most meaningful hypotheses, but the experiment did suggest that conscious experience involves continual activity of neurons at the back of the brain. According to the experts, this finding fits IIT better than the alternative, but only narrowly, and not in a way that could be said to elevate it above all other theories of consciousness. Still, any public perception that IIT had achieved an empirical triumph galled Lau, and when the results were covered in Science, Nature, and The New York Times, it tipped him over the edge.

“I didn’t want to act alone,” Lau told me. He drafted a letter criticizing IIT and sent it to another scientist who shared his dim view of the theory. Over the next six weeks, they worked on revisions, before passing the letter on to eight more scientists for further edits. After this core group had settled on a final version, they began distributing it more widely. This time, there was no request for edits; just signatures. Word of the letter began to spread, even among those who had not been asked to sign. When at last the preprint was released, its 124 signatories included neuroscientists, behavioral scientists, philosophers, and psychologists.

Despite all the effort that went into its creation, the letter was, admittedly, thin on substance. Running just five paragraphs in all, its first half takes aim not at the scientific underpinnings of IIT, but rather at the ways in which the theory is portrayed in news media. It complains that the reporters who covered the initial findings from the adversarial experiments falsely anointed IIT the “dominant” theory of consciousness; and it describes the public as having been victimized by “scientific misinformation.” But as Erik Hoel, who completed his doctorate in neuroscience under Tononi, has pointed out, none of the five media sources cited in the letter say anything of the kind. The first news story mentioned is headlined “Consciousness Hunt Yields Results, but Not Clarity.” Hoel told me that he read through each of the others, and although one did say that IIT “has a leg up,” it qualified that there were still “continuing doubts” about the results.”

The letter’s second half calls out IIT for having “panpsychist commitments,” and says that because the theory’s core claims are untestable it should be thought of as a “pseudoscience,” like astrology. “A lot of the people who signed on to the letter were a little uncomfortable with the use of that word,” one of the signatories, Joshua Shepherd, a philosophy professor at Carleton University, in Canada, told me. “If you’re going to make a strong claim like that, then you have to give some very strong evidence,” David Chalmers, a professor at NYU and one of the foremost philosophers of consciousness, told me. “Given the 100-plus very well-known figures who signed the letter, I was expecting something more solid, and I think a lot of people had reactions like that.” Seth told me he was surprised by the list of names at the bottom of the letter. “I know that some of them know nothing about IIT and probably didn’t know what they were signing,” he said.

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The online backlash was immediate. On X (formerly Twitter), scientists derided the letter as a “childish” product of “intellectual dishonesty.” It was called “shameless mudslinging” and a “hit” job. One scientist complained that cancel culture had now come for ideas. Others suggested that the letter had been motivated by politics or even financial interests. The conflict spilled over into dueling edits on Wikipedia, concerning whether IIT should be tagged as a pseudoscience. At least one scientist who signed the letter says that he received an email warning of “personal and professional consequences.” Lau himself complained that an angry mob was out to get him, and was in turn accused of playing the victim.

Several experts told me that the letter’s inclusion of Daniel Dennett, a longtime heavyweight in the field, was significant. Hoel was unfazed, however. “Dennett is not really on the front lines anymore,” he said. IIT was being punished, he continued, for daring to be a formal mathematical theory. Other, story-based theories of consciousness don’t offer any precise mathematical model of consciousness that an experiment could locate. How is someone supposed to tell which theory is pseudoscience and which isn’t? One observer likened the situation to a bunch of people standing on step ladders in a field arguing over who is closest to the moon.

Critics of the letter argued that the field should be keeping up appearances, for the sake of continued funding. (In a way, their concern mirrors Lau’s own.) Seth told me that claims of pseudoscience risk giving ammunition to people who are already skeptical. Chalmers agreed: “If funders look on and they say, ‘This is a field where half the people are calling the other half pseudoscientists,’ I worry that this could have implications for everybody.” On social media, he went so far as to compare using the “pseudoscience” tag to dropping a nuclear bomb in order to settle a regional dispute.

Lau, who lives in Japan, called this talk of nuclear war “unhinged” and insensitive. He said that he’d tried taking a more diplomatic tack before drafting the letter, but it didn’t work. Some years ago, he told me, he’d written to Christof Koch, an investigator at the Allen Institute, in Seattle, and one of the most visible proponents of IIT, to try to clear the air. (Among other things, Lau hadn’t liked it when Koch told The New York Times that IIT is “the only really promising fundamental theory of consciousness.”) Lau suggested a Zoom call, and even offered to fly to Seattle for a meeting face-to-face. “Koch said he was too busy.”

Lau does feel bad that the letter sowed such chaos, but he stopped short of expressing regrets. “I stand by everything,” he said. On our last call, he was still insisting that the scientists who work on IIT are the ones who should be soul-searching. “If one-third of the community told me my work is pseudoscience, I would do some reflection,” he said. “Oh?” I asked. “Maybe I would get angry first,” he acknowledged, “but then I would reflect.”

So far, there’s little evidence of reflection, on anyone’s part. I asked Chalmers, who has a wider network in the field than just about anybody, when the conflict might be resolved. He said that he didn’t know, and that emotions are still running high: “I don’t think [we’re] ready for a kumbaya moment just yet.”