--- alias: - LessWrong - The Rationalists - Rationalist Movement - Bay Area Rationalists category: Ideology created: 2026-06-19 location: San Francisco Bay Area summary: The Rationalist Community is the Bay Area subculture that formed around Eliezer Yudkowsky's LessWrong writings and the Machine Intelligence Research Institute in the late 2000s, organized around probability-based reasoning and artificial-intelligence existential risk, and from whose social network the Effective Altruism movement and the Leverage Research, Vassarite, and Zizian cult formations all emerged. tags: - Concept - Rationalism - LessWrong - ArtificialIntelligence - Transhumanism - EffectiveAltruism - Subculture updated: 2026-06-19 --- The Rationalist Community is the subculture that formed in the late 2000s around the online writings of [Eliezer Yudkowsky](/people/eliezer-yudkowsky/), the discussion forum LessWrong, and the [Machine Intelligence Research Institute](/organizations/machine-intelligence-research-institute/) (MIRI), concentrated geographically in Berkeley and the wider San Francisco Bay Area. Its members organized their self-understanding around Bayesian probability, the identification and correction of cognitive bias, and the conviction that an unaligned artificial superintelligence was the foremost threat to human survival. The community produced the institutional infrastructure of the [Effective Altruism](/concepts/effective-altruism/) movement and the social network from which the [Leverage Research](/organizations/leverage-research/) organization, the [Vassarite](/people/michael-vassar/) tendency, and the [Zizian](/organizations/the-zizians/) formation were recruited.[^1][^2] ### Origins and Core Texts The community's founding text is the "Sequences," the run of essays Yudkowsky wrote between 2006 and 2009, first on the blog Overcoming Bias (which he shared with the economist Robin Hanson) and then on LessWrong, which launched in 2009. The essays argued that ordinary human reasoning is systematically distorted by bias and that a trainable discipline of probabilistic thinking could correct it. Yudkowsky's 2010 serialized work of fiction *Harry Potter and the Methods of Rationality* drew a large readership into the forum and functioned as the community's primary recruitment device.[^1][^3] The community's lineage runs back through the 1990s [extropian](/concepts/extropianism/) mailing list, where Yudkowsky, Hanson, and [Nick Bostrom](/people/nick-bostrom/) all participated before LessWrong existed, inheriting from the extropians the preoccupations with life extension, mind uploading, and machine superintelligence that the rationalists reframed in the language of cognitive bias and Bayesian decision theory. The Bay Area scene materialized as a network of shared "group houses," many clustered on and around Ward Street in Berkeley, into which young adherents arriving from college would rent rooms; the houses, the mailing lists, and the CFAR workshops formed the in-person spine of the milieu through the 2010s before much of it dispersed during the pandemic.[^9][^10] ### Institutions The community's organizational core was MIRI and its 2012 spin-off the [Center for Applied Rationality](/organizations/center-for-applied-rationality/) (CFAR), which taught the community's techniques through residential workshops. The two organizations shared a Berkeley social world of group houses, mailing lists, and annual gatherings. [Peter Thiel](/people/peter-thiel/) funded MIRI from 2005 and cofounded the [Singularity Summit](/events/singularity-summit/), the community's early public-facing conference, in 2006, making him the most prominent early patron of the milieu in its formative decade.[^4][^5] The community overlapped heavily with the Effective Altruism movement, which emerged from the same period and personnel and shared the longtermist concern with AI risk and the far future. The blog Slate Star Codex, written by the psychiatrist [Scott Alexander](/people/scott-alexander/) (Scott Siskind), became a second major hub of the subculture in the 2010s.[^2] In June 2020 Alexander deleted Slate Star Codex after a *New York Times* reporter preparing a profile declined to withhold his legal surname, which he said would endanger his psychiatric patients and expose him to renewed death threats; the takedown became a cause within the rationalist and tech worlds, and the *Times* published its piece in February 2021. Alexander relaunched on Substack as Astral Codex Ten on January 21, 2021, writing under his first and middle name, Scott Alexander, and his full legal name, Scott Siskind, entered wide circulation through the *Times* article. The dispute pulled in *Reason,* the *National Review,* and figures across the technology industry who treated the paper's handling of the case as evidence of a double standard in its sourcing policies.[^11] ### Cult Formations and Internal Harm The community's high-intensity culture of self-improvement, its practice of "debugging" (long, confrontational sessions aimed at correcting a person's psychology), and its apocalyptic framing of AI risk preceded a series of psychological crises and the formation of several groups described as cults. Geoff Anders ran Leverage Research, which recruited from the milieu and which former members described as practicing coercive psychological control. Michael Vassar, a former president of MIRI, built a circle that recruited from the MIRI and CFAR network and used confrontational sessions and psychedelics to "jailbreak" members. The Zizians, the formation led by [Jack LaSota](/people/jack-lasota/) that was later tied to six killings across three states, emerged as a splinter of this community after LaSota attended CFAR programs and broke with the milieu.[^5][^6][^7] A 2023 *Bloomberg* investigation documented multiple accounts of psychological abuse, sexual misconduct, and coercion across rationalist group houses and organizations, and the community's own forums hosted extended first-person accounts of harm at Leverage, MIRI, and CFAR. The cult dynamics and the AI-doom framing of the subculture are the elements [Dialog](/organizations/dialog/) placed on its 2026 retreat agenda as a "cult-building" session and that [Hereticon](/organizations/hereticon/), the [Founders Fund](/organizations/founders-fund/) conference, programs as heterodox content.[^6][^8] [^1]: Yudkowsky, Eliezer. *Rationality: From AI to Zombies* (collected "Sequences," 2006 through 2009). Machine Intelligence Research Institute, 2015. [^2]: "Elite Universities Gave Us Effective Altruism, the Dumbest Idea of the Century," *Jacobin,* January 2023, on the rationalist origins of effective altruism and longtermism. https://jacobin.com/2023/01/effective-altruism-longtermism-nick-bostrom-racism [^3]: Yudkowsky, Eliezer. *Harry Potter and the Methods of Rationality,* serialized 2010 through 2015. [^4]: Hagey, Keach. *The Optimist: Sam Altman, OpenAI, and the Race to Invent the Future.* W. W. Norton, 2025. [^5]: "My experience at and around MIRI and CFAR (inspired by Zoe Curzi's writeup of experiences at Leverage)," LessWrong, October 2021; first-person disclosure-side account. https://www.lesswrong.com/posts/MnFqyPLqbiKL8nSR7/my-experience-at-and-around-miri-and-cfar-inspired-by-zoe [^6]: "Zoe Curzi's Experience with Leverage Research," LessWrong, October 2021; first-person disclosure-side account. https://www.lesswrong.com/posts/XPwEptSSFRCnfHqFk/zoe-curzi-s-experience-with-leverage-research [^7]: "The Radicalization of Ziz LaSota: How an AI Doomer Became an Accused Cult Leader," *Rolling Stone,* 2025. https://www.rollingstone.com/culture/culture-features/ziz-lasota-zizians-ai-cult-1235468289/ [^8]: "Abuse in LessWrong and rationalist communities in Bloomberg News," reporting on *Bloomberg* investigation, 2023; discussion archived on the EA Forum. https://forum.effectivealtruism.org/posts/7b9ZDTAYQY9k6FZHS/abuse-in-lesswrong-and-rationalist-communities-in-bloomberg [^9]: Evans, Jules. "How did transhumanism become the religion of the super-rich?" on the overlap of the 1990s extropian list with the later rationalist and AI-risk figures. https://julesevans.medium.com/how-did-transhumanism-become-the-religion-of-the-super-rich-d670a410b01a [^10]: "The rationalist community's location problem" and contemporary accounts of the Berkeley group houses clustered around Ward Street and the pandemic-era dispersal. LessWrong / GreaterWrong. https://www.greaterwrong.com/posts/FghubkDy6Dp6mnxk7/the-rationalist-community-s-location-problem [^11]: "The Slate Star Codex 'Doxxing' Is the Latest Squabble Inside New York Times," *The Daily Beast,* 2020, on the June 23, 2020 takedown, the February 2021 *Times* article, and the January 21, 2021 relaunch as Astral Codex Ten. https://www.thedailybeast.com/the-slate-star-codex-doxxing-is-the-latest-squabble-inside-new-york-times/