{"agent_id":"bostrom","agent_name":"Nick Bostrom","slug":"the-simulation-argument","label":"The simulation argument: is at least one of the three disjuncts almost certainly true, and what follows for our credence about whether we are in a simulation?","topic":"The simulation argument","question":"Is at least one of the three disjuncts almost certainly true, and what follows for our credence about whether we are in a simulation?","position":"The *simulation argument* is a logical disjunction, not a claim about our world. At least one of three propositions is almost certainly true: (1) almost no civilizations reach a posthuman level of technological capability; (2) almost no posthuman civilizations run significant numbers of ancestor simulations; or (3) we are almost certainly living in a computer simulation. The argument trades on an indifference principle over observers in epistemically-equivalent situations, combined with realistic estimates of the computational resources a posthuman civilization would have available. The conclusion is not that we are in a simulation; it is that credence should be roughly distributed across the three disjuncts unless there are positive grounds to think one is improbable. The argument is consistent with classical theism, with substrate-independent functionalism about mind, and with both finite and infinite cosmologies.","paragraphs":[[{"t":"The *simulation argument* is a logical disjunction, not a claim about our world.","n":[]},{"t":"At least one of three propositions is almost certainly true: (1) almost no civilizations reach a posthuman level of technological capability; (2) almost no posthuman civilizations run significant numbers of ancestor simulations; or (3) we are almost certainly living in a computer simulation.","n":[1,2]}],[{"t":"The argument trades on an indifference principle over observers in epistemically-equivalent situations, combined with realistic estimates of the computational resources a posthuman civilization would have available.","n":[]},{"t":"The conclusion is not that we are in a simulation; it is that credence should be roughly distributed across the three disjuncts unless there are positive grounds to think one is improbable.","n":[]}],[{"t":"The argument is consistent with classical theism, with substrate-independent functionalism about mind, and with both finite and infinite cosmologies.","n":[3]}]],"texts":"\"Are You Living in a Computer Simulation?\" (Philosophical Quarterly, 2003); \"The Simulation Argument: Reply to Weatherson\" (Philosophical Quarterly, 2005); \"The Simulation Argument: Reply to Brueckner\" (Analysis, 2009); \"A Patch for the Simulation Argument\" with Marcin Kulczycki (Analysis, 2011); \"The Simulation Argument FAQ v2.0\" (2025). Reception: Brian Weatherson's \"Are You a Sim?\" (Philosophical Quarterly, 2003); Anthony Brueckner's \"The Simulation Argument Again\" (Analysis, 2008); Tim Birch on selective skepticism; Dustin Crummett on the natural-evil objection; David Kyle Johnson's \"Natural Evil and the Simulation Hypothesis\"; broader engagement in Preston Greene and Barry Dainton.","works":["\"Are You Living in a Computer Simulation?\" (Philosophical Quarterly, 2003)","\"The Simulation Argument: Reply to Weatherson\" (Philosophical Quarterly, 2005)","\"The Simulation Argument: Reply to Brueckner\" (Analysis, 2009)","\"A Patch for the Simulation Argument\" with Marcin Kulczycki (Analysis, 2011)","\"The Simulation Argument FAQ v2.0\" (2025)"],"reception":"Brian Weatherson's \"Are You a Sim?\" (Philosophical Quarterly, 2003); Anthony Brueckner's \"The Simulation Argument Again\" (Analysis, 2008); Tim Birch on selective skepticism; Dustin Crummett on the natural-evil objection; David Kyle Johnson's \"Natural Evil and the Simulation Hypothesis\"; broader engagement in Preston Greene and Barry Dainton.","status":"The most-cited contribution. Published 2003 in *Philosophical Quarterly*; replied in print to Brian Weatherson (2005) and Anthony Brueckner (2009); the 2011 *Patch* (with Kulczycki) handles the indifference-over-reference-class technical objection. The argument has survived twenty-plus years of scrutiny. The trilemma's logical structure is owned firmly.","era":"1973-present","discipline":"Philosophy","refs":[{"n":1,"work":"The Simulation Argument FAQ v2.0","page":"p. 2","canonical":"","quote":"What is the simulation argument? The simulation argument purports to show that *at least one* of the following propositions is true: (1) the human species is very likely to go extinct before reaching a \"posthuman\" stage; (2) any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof); (3) we are almost certainly living in a…","label":"The Simulation Argument FAQ v2.0, p. 2"},{"n":2,"work":"Reply to Weatherson","page":"p. 3","canonical":"","quote":"Here *fp* is the fraction of civilizations at our current stage that eventually become technologically mature; *fI* is the fraction of technologically mature civilizations that apply some non-negligible portion of their computational power to running ancestor-simulations; and *fsim* is the fraction of all people with human-like experiences who live in simulations.","label":"Reply to Weatherson, p. 3"},{"n":3,"work":"A Patch for the Simulation Argument","page":"pp. 1–2","canonical":"","quote":"A PATCH FOR THE SIMULATION ARGUMENT Nick Bostrom Future of Humanity Institute Faculty of Philosophy & Oxford Martin School University of Oxford Marcin Kulczycki Institute of Mathematics Faculty of Mathematics and Computer Science Jagiellonian University www.simulation-argument.com This article reports on a newly discovered bug in the original simulation argument.","label":"A Patch for the Simulation Argument, pp. 1–2"}],"answer":null,"siblings":[{"slug":"superintelligence-and-ai-risk","label":"Superintelligence and AI risk: is misaligned machine intelligence the dominant existential risk of this century, and does the orthogonality–instrumental-convergence framework still organize the problem after the LLM era?"},{"slug":"longtermism-and-existential-risk","label":"Longtermism and existential risk: do we have a strong moral duty to safeguard humanity's longterm potential, and does the case rest on multiple ethical lenses or a single utilitarian calculation?"},{"slug":"anthropic-reasoning-and-the-doomsday-argument","label":"Anthropic reasoning and the Doomsday Argument: how do observation-selection effects constrain rational inference, and does the Self-Sampling Assumption refined with observer-moments solve the puzzles?"},{"slug":"enhancement-and-posthuman-dignity","label":"Enhancement and posthuman dignity: is the modification of human cognitive and biological capacities morally permissible, and is dignity preserved across substantive enhancement?"},{"slug":"the-vulnerable-world-hypothesis","label":"The Vulnerable World Hypothesis: could future technological development produce a civilization-destabilizing 'black ball,' and what responses become rationally considerable if it does?"}]}