The very online ‘gray tribe’ philosophy of alleged UnitedHealthcare killer Luigi Mangione

The man accused of killing Brian Thompson had an extensive social media history that makes his worldview very clear, writes Io Dodds

The man accused of killing UnitedHealthcare CEO Brian Thompson followed Richard Dawkins and RFK Jr, tweeted about neuroscience and Japanese birth rates, and shared posts about how to think more logically.

The 26-year-old was fascinated by AI and decision theory; pro-technology but anti-smartphones; secular and scientific in his outlook, but in favour of religion on Darwinian grounds.

What does it all mean? Luigi Mangione's worldview might not be familiar to most Americans, and it's certainly not a common one among politically-motivated killers. Nevertheless, his social media posts, and the users he engaged with, mark him out indelibly as a very specific type of online person – one that's intimately familiar to me.

”Increasingly looks like we've got our first gray tribe shooter, and boy howdy is the media not ready for that,” wrote the journalist and extremism expert Robert Evans, who analysed Mangione’s online life earlier this week.

There's no single accepted name for this loose, extremely online subculture of bloggers, philosophers, shitposters and Silicon Valley coders. "The gray tribe” is one term; ”the rationalist movement” is another.

First, let me stress: so far, there’s little evidence that this worldview inspired Thompson's killing, at least directly. Unlike more usual suspects like neo-Nazis or Islamic jihadists, gray tribe thinkers rarely preach armed insurrection, and are more likely to advocate social change through high-quality randomized controlled studies.

Moreover, violent acts are never the consequence of ideology alone. Mangione hadn’t tweeted since June, and it’s unclear where he has lived or what he has done in the last few months. Mangione had recently dropped out of contact with his friends and family, and appears to have suffered from “life-halting” chronic pain. These factors should complicate any simple assumptions about any potential motivation.

What the 26-year-old Ivy Leaguer’s online history does give us is an insight into his intellectual background – and, perhaps, the prism through which he viewed his decisions.

The term "gray tribe" comes from a 2014 essay by Scott Alexander, a California psychiatrist and blogger whose influence on rationalist subculture is hard to understate. Intended as contrast to America's "blue tribe" and "red tribe" (generally, Democrats and Republicans), it gave a snappy name to the nebula of "libertarianish tech-savvy nerds" that had grown out of a handful of noughties blogs and forums.

Gray tribers tend be self-consciously intellectual and open-minded, preoccupied with learning how to overcome their own mental biases. They're deliberately eclectic in their information diet, invoking esoteric ideas from many different fields. They often gravitate towards numbers and statistics.

Many work in tech, like Mangione did until recently. Some see themselves as "high decouplers", who are adept at disconnecting emotion and social context from the intellectual questions they consider. Many happen to be autistic. They are also ideologically diverse and highly fractious, which makes all of the above a severe generalization.

Mangione's posts on X, formerly Twitter, fit this mold pretty well. Like many rationalists he talked a lot about metacognition (that is, thinking about thinking), regularly posting and sharing posts about logical errors, confirmation bias, and other quirks of the human mind.

He also apparently loves mathematics, at one point posting (by my count) 127 nearly identical tweets featuring unique random numbers. "I used to get bummed in math class when learning theorems," he wrote in January, "[because] all the low-hanging fruit has been solved before I was born."

Even his alleged manifesto includes citations, appeals to statistics, and a disclaimer that “obviously the problem [of health insurance] is more complex” than he has time to describe.

Other common topics included new technologies such as AI, lab-grown food, utilitarian ethics, and the Singularity (a hypothesised future point at which AI irrevocably escapes human control).

“When we understand just how fast the rate of human progress is increasing, a revolutionary future... is the only logical conclusion,” he said in a speech at high school. “Today’s careers may be drastically changed or even eliminated in 30 years.”

Grays are often systems thinkers, who take pride in attributing social problems not to individual evil but to complex interplays of incentives and institutions. Just so, Mangione often dissected issues in terms of "emergent" consequences of "selective pressures" and "amorphous systems outside of our control".

His explanations were frequently Darwinian, such as when he argued that Christianity had prospered because it enhanced humankind’s evolutionary fitness or that Japan’s birth rates are low because its “urban environment is an evolutionary mismatch for the human animal”. (The latter post also suggests he may be a bit of a weeb, because who else cares so much about maid cafes and grocery store sex toys?)

From analysing his timeline, I’d put Mangione loosely on the political right of this coalition His posts and shares are highly concerned with cancel culture and "wokeness", and seem to take a traditionalist stance on the natural roles of men and women. (Like all men, allegedly, he often thought about the Roman Empire.)

In some of these tweets and retweets there is a palpable sense of being adrift, of anomie (instability after a breaking down of social norms), all of which is often dicussed as common for young men these days. "Netflix, DoorDash, and true crime podcasts have stolen more dreams than failure ever will,” read one post he shared on X.

He also followed Beff Jezos, aka Guillaume Verdon, a doyen of the self-styled “effective accelerationist” movement that seeks to unchain AI from all human restraint to create a technocapitalist singularity. After his arrest, some gray tribers identified him as part of the right-leaning rationalist and “postrationalist” network often called “this part of Twitter”, or “TPOT” .

Mangione’s leanings are obvious to me because I too spent many years with one foot in rationalist subculture. Though I never considered myself part of the “tribe”, its ideas shaped the way I think even when I disagreed with them. Just ask my friends how often I answer questions using Bayesian probability.

This philosophy isn't without its critics. Scholars such as Émile P Torres and Timnit Gebru have challenged the gray tribe’s frequent fixation on intelligence and its penchant for hyper-utilitarian ethics, arguing that the community is rife with racist assumptions dressed up as dispassionate logic.

But most of that discussion has focused on rationalism's prevalence in Silicon Valley, and on the outsize influence its adherents therefore enjoy over billions of people’s daily lives and the technology they use. A rationalist assassinwould be something else entirely.

Mangione, of course, is innocent until proven guilty.