Simulation hypothesis

In 2003, philosopher Nick Bostrom proposed a trilemma that he called "the simulation argument". Despite the name, Bostrom's "simulation argument" does not directly argue that we live in a simulation; instead, Bostrom's trilemma argues that one of three unlikely-seeming propositions is almost certainly true:

1. "The fraction of human-level civilizations that reach a posthuman stage (that is, one capable of running high-fidelity ancestor simulations) is very close to zero", or
2. "The fraction of posthuman civilizations that are interested in running simulations of their evolutionary history, or variations thereof, is very close to zero", or
3. "The fraction of all people with our kind of experiences that are living in a simulation is very close to one."

The trilemma points out that a technologically mature "posthuman" civilization would have enormous computing power; if even a tiny percentage of them were to run "ancestor simulations" (that is, "high-fidelity" simulations of ancestral life that would be indistinguishable from reality to the simulated ancestor), the total number of simulated ancestors, or "Sims", in the universe (or multiverse, if it exists) would greatly exceed the total number of actual ancestors.

Bostrom goes on to use a type of anthropic reasoning to claim that, if the third proposition is the one of those three that is true, and almost all people with our kind of experiences live in simulations, then we are almost certainly living in a simulation.

Bostrom claims his argument goes beyond the classical ancient "skeptical hypothesis", claiming that "...we have interesting empirical reasons to believe that a certain disjunctive claim about the world is true", the third of the three disjunctive propositions being that we are almost certainly living in a simulation. Thus, Bostrom, and writers in agreement with Bostrom such as David Chalmers, argue there might be empirical reasons for the "simulation hypothesis", and that therefore the simulation hypothesis is not a skeptical hypothesis but rather a "metaphysical hypothesis". Bostrom states he personally sees no strong argument as to which of the three trilemma propositions is the true one: "If (1) is true, then we will almost certainly go extinct before reaching posthumanity. If (2) is true, then there must be a strong convergence among the courses of advanced civilizations so that virtually none contains any individuals who desire to run ancestor-simulations and are free to do so. If (3) is true, then we almost certainly live in a simulation. In the dark forest of our current ignorance, it seems sensible to apportion one's credence roughly evenly between (1), (2), and (3)... I note that people who hear about the simulation argument often react by saying, 'Yes, I accept the argument, and it is obvious that it is possibility #n that obtains.' But different people pick a different n. Some think it obvious that (1) is true, others that (2) is true, yet others that (3) is true."

As a corollary to the trilemma, Bostrom states that "Unless we are now living in a simulation, our descendants will almost certainly never run an ancestor-simulation."[3][4][5][6]

Bostrom argues that if "the fraction of all people with our kind of experiences that are living in a simulation is very close to one", then it follows that we probably live in a simulation. Some philosophers disagree, proposing that perhaps "Sims" do not have conscious experiences the same way that unsimulated humans do, or that it can otherwise be self-evident to a human that they are a human rather than a Sim.[4][7] Philosopher Barry Dainton modifies Bostrom's trilemma by substituting "neural ancestor simulations" (ranging from literal brains in a vat, to far-future humans with induced high-fidelity hallucinations that they are their own distant ancestors) for Bostrom's "ancestor simulations", on the grounds that every philosophical school of thought can agree that sufficiently high-tech neural ancestor simulation experiences would be indistinguishable from non-simulated experiences. Even if high-fidelity computer Sims are never conscious, Dainton's reasoning leads to the following conclusion: either the fraction of human-level civilizations that reach a posthuman stage and are able and willing to run large numbers of neural ancestor simulations is close to zero, or we are in some kind of (possibly neural) ancestor simulation.[8]

Some scholars categorically reject—or are uninterested in—anthropic reasoning, dismissing it as "merely philosophical", unfalsifiable, or inherently unscientific.[4]

Some critics propose that we could be in the first generation, and all the simulated people that will one day be created do not yet exist.[4]

The cosmologist Sean M. Carroll argues that the simulation hypothesis leads to a contradiction: if we are typical, as it is assumed, and we are not capable of performing simulations, this contradicts the arguer's assumption that it is easy for us to foresee that other civilizations can most likely perform simulations.[9]

Physicist Frank Wilczek raises an empirical objection, saying that the laws of the universe have hidden complexity which is "not used for anything" and the laws are constrained by time and location -- all of this being unnecessary and extraneous in a simulation. He further argues that the simulation argument amounts to "begging the question," due to the "embarrassing question" of the nature of the underlying reality in which this universe is simulated. "Okay if this is a simulated world, what is the thing in which it is simulated made out of? What are the laws for that?"[10]

Some scholars accept the trilemma, and argue that the first or second of the propositions are true, and that the third proposition (the proposition that we live in a simulation) is false. Physicist Paul Davies deploys Bostrom's trilemma as part of one possible argument against a near-infinite multiverse. This argument runs as follows: if there were a near-infinite multiverse, there would be posthuman civilizations running ancestor simulations, and therefore we would come to the untenable and scientifically self-defeating conclusion that we live in a simulation; therefore, by reductio ad absurdum, existing multiverse theories are likely false. (Unlike Bostrom and Chalmers, Davies (among others) considers the simulation hypothesis to be self-defeating.)[4][11]

Some point out that there is currently no proof of technology which would facilitate the existence of sufficiently high-fidelity ancestor simulation. Additionally, there is no proof that it is physically possible or feasible for a posthuman civilization to create such a simulation, and therefore for the present, the first proposition must be true.[4] Additionally there are limits of computation.[3][12]

Physicist Marcelo Gleiser objects to the notion that posthumans would have a reason to run simulated universes: "...being so advanced they would have collected enough knowledge about their past to have little interest in this kind of simulation. ...They may have virtual-reality museums, where they could go and experience the lives and tribulations of their ancestors. But a full-fledged, resource-consuming simulation of an entire universe? Sounds like a colossal waste of time." Gleiser also points out that there is no plausible reason to stop at one level of simulation, so that the simulated ancestors might also be simulating their ancestors, and so on, creating an infinite regress akin to the "problem of the First Cause."[13]

Science fiction has highlighted themes such as virtual reality, artificial intelligence and computer gaming for more than fifty years. Jokester (1956) by Isaac Asimov explores the idea that humour is actually a psychological study tool imposed from without by extraterrestrials studying mankind, similarly to how humans study mice. Simulacron-3 (1964) by Daniel F. Galouye (alternative title: Counterfeit World) tells the story of a virtual city developed as a computer simulation for market research purposes, in which the simulated inhabitants possess consciousness; all but one of the inhabitants are unaware of the true nature of their world. The book was made into a German made-for-TV film called World on a Wire (1973) directed by Rainer Werner Fassbinder. The movie The Thirteenth Floor (1999) was also loosely based on this book. "We Can Remember It for You Wholesale" is a short story by American writer Philip K. Dick, first published in The Magazine of Fantasy & Science Fiction in April 1966, and was the basis for Total Recall (1990 film) and Total Recall (2012 film). In Overdrawn at the Memory Bank, a 1983 television movie, the main character pays to have his mind connected to a simulation.

The 1993 Star Trek: The Next Generation episode "Ship in a Bottle" explores the idea of people being unaware they are living in simulation, with Picard postulating at the end that perhaps they are also in a simulation playing out in a box on a table. This is also a possible use of dramatic irony, with both the actors and audience aware the television programme is indeed a simulation of sorts.

The same theme was repeated in the 1999 film The Matrix, which depicted a world in which artificially intelligent robots enslaved humanity within a simulation set in the contemporary world. The 2012 play World of Wires was partially inspired by the Bostrom essay on the simulation hypothesis.[23] In the episode "Extremis" (broadcast on 20 May 2017 on BBC One) of the science fiction series Doctor Who, aliens called "The Monks" plan an invasion of Earth by running and studying a holographic simulation of Earth with conscious inhabitants. When the virtual Doctor finds out about the simulation he sends an email about the simulation to his real self so that the real Doctor can save the world. In the first season of Rick and Morty, a science-fiction animated comedy, the episode "M. Night Shaym-Aliens!" (2014) aliens trap the lead role (Rick) in a simulated reality in order to trick him into revealing his formula for concentrated dark matter. The hypothesis also serves as the climax of No Man's Sky's overarching plot, in which it was revealed that the game's setting itself was a simulation and that the player character is a member of a race made to explore it. In the game Xenoblade Chronicles, it is revealed that the whole world of the gods Bionis and Mechonis was a simulation run by Alvis, the administrative computer of a phase transition experiment facility (heavily implied to be "Ontos" in Xenoblade Chronicles 2) after Klaus destroyed the universe in a multiverse experiment.