The simulation hypothesis or simulation theory is the proposal that all of reality, including the Earth and the rest of the universe, could in fact be an artificial simulation, such as a computer simulation. Some versions rely on the development of a simulated reality, a proposed technology that would be able to convince its inhabitants that the simulation was "real". The simulation hypothesis bears a close resemblance to various other skeptical scenarios from throughout the history of philosophy. The hypothesis was popularized in its current form by Nick Bostrom. The suggestion that such a hypothesis is compatible with all of our perceptual experiences is thought to have significant epistemological consequences in the form of philosophical skepticism. Versions of the hypothesis have also been featured in science fiction, appearing as a central plot device in many stories and films.
There is a long philosophical and scientific history to the underlying thesis that reality is an illusion. This skeptical hypothesis can be traced back to antiquity; for example, to the "Butterfly Dream" of Zhuangzi, or the Indian philosophy of Maya, or in Ancient Greek philosophy Anaxarchus and Monimus likened existing things to a scene-painting and supposed them to resemble the impressions experienced in sleep or madness.
A version of the hypothesis was also theorised as a part of a philosophical argument by René Descartes.
Nick Bostrom's premise:
Many works of science fiction as well as some forecasts by serious technologists and futurologists predict that enormous amounts of computing power will be available in the future. Let us suppose for a moment that these predictions are correct. One thing that later generations might do with their super-powerful computers is run detailed simulations of their forebears or of people like their forebears. Because their computers would be so powerful, they could run a great many such simulations. Suppose that these simulated people are conscious (as they would be if the simulations were sufficiently fine-grained and if a certain quite widely accepted position in the philosophy of mind is correct). Then it could be the case that the vast majority of minds like ours do not belong to the original race but rather to people simulated by the advanced descendants of an original race.
Nick Bostrom's conclusion:
It is then possible to argue that, if this were the case, we would be rational to think that we are likely among the simulated minds rather than among the original biological ones.
Therefore, if we don't think that we are currently living in a computer simulation, we are not entitled to believe that we will have descendants who will run lots of such simulations of their forebears.— Nick Bostrom, Are You Living in a Computer Simulation?, 2003
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:
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."
Further information: Anthropic principle
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. 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.
Some scholars categorically reject—or are uninterested in—anthropic reasoning, dismissing it as "merely philosophical", unfalsifiable, or inherently unscientific.
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.
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.
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?"
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 use 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.)
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. Additionally there are limits of computation.
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."
In physics, the view of the universe and its workings as the ebb and flow of information was first observed by Wheeler. This shift of paradigm from understanding the universe as energy transformation to the information processing universe leads to the emergence of a new branch of science called quantum computation. Quantum evolution of a system is represented in quantum computation by a quantum circuit built from quantum gates. Consequently, two views of the world emerged, the first one, proposes that the universe is a quantum computerand the other one proposes that the system performing the simulation is distinct from its simulation (the universe). Recently, another possibility is proposed, which is a “hybrid” between the two propositions based on the following assumptions
Under the assumption of finite computational resources, the simulation of the universe would be performed by dividing the continuum spacetime into a discrete set of points. Many physical aspects can support the simulation hypothesis, e:g:,
Many physical results can be derived from the above description of the world, e.g.
Time travel paradox, antimatter, and others physical phenomenon can have their interpretation within the simulation hypothesis.
Inspired by the many world interpretation of quantum mechanics  and the subjective idealism view of reality, the author of hypothesize the evolution of the universe in the following fashion: a cosmological consciousness being equipped with thinking tools that include inductive, deductive, and abductive reasoning, etc., and other types of thinking  created/simulated the universe and start injecting random qubits, “quantum fluctuation”, into the baby universe where information gets processed. By observing/measuring the results a new quantum circuits can be exited and the cycle repeat through a feedback loop in a process similar to the working of the brain where the born rule can be compared to the weights in the neural network. As the system evolves subsystems emerge each of which has its own computation abilities and functionalities. This construction is reminiscent to the so called the Game of Life (GOL) which is a cellular automaton invented by Conway. Although, the fundamental “physics” of this world is so simple, as the game evolve, and at different scales, new “physics”, “chemistry” and “biology” emerges. In fact, by choosing an appropriate initial configuration of the game, complex system emerges and Self-replication object can appear, even more surprising, emerging laws could entail new concepts and entities which do not “apparently” exist in the original laws . In a more abstract way, this construction of the universe can be imagined as each cognitive subsystem is equipped with a formal language that “lives” in a metalanguage  and having finite set of axioms (obviously not complete ) that define its dynamics according to some interpretation (model dependent reality) and evolves into different forms. Furthermore, this world can be decomposed into three types of entities, the inorganic matter which is small structure uses simple quantum logic gates that determine its evolution, the organic matter which acquire more computational abilities for learning and human that has ability for reasoning. Space and time and physical laws can be thought of, in a Kantian language , as a type of relations in a mathematical structure and matter is a realization/support of this “philosophical matter” . Evolution in this structure can be imagined as a process of mind from state to another state which can be translated in the material world into a Turing machines (TM) where logical statements about proofs are translated into actions of machines. Note that, even though TM are built from a simple logic gates they are able to simulate a very sophisticated video game like World of Warcraft and Fortnite. The difference between modern computers that are built upon the Von Neumann architecture of TM and the universal computation is that TM uses deterministic computation, however, universal computation uses quantum computation to explore the whole spectrum of computation which gives the system the ability to evolve by learning and making decisions. This imagination about the universe formation is similar to Von Neumann method of creating natural numbers out of empty sets who imagined that all numbers could be bootstrapped out of the empty set by the operations of the mind. In a platonic sense, that is in the world of ideas, each partition of the world would evolve by increasing its content toward the infinity or decreasing toward the emptiness or it can be locked in a minima. Therefore, attention, play a major role in this approach which depends on the system “personalities” . Furthermore, the driving force for a subsystem to grow, that is to increase its knowledge base, is speculated as the “force of love”  which, in a systemic view translate into creativity and novelty (this aspect is included in a video game  ). This construction can be compared to computational ontology, used in semantic web, which defines a set of representational primitives with which to model a domain of knowledge or discourse. The representational primitives are typically classes (or sets), attributes (or properties), and relationships (or relations among class members). Computational ontology uses description logic for reasoning and it is used to model genetic ontology, emotion ontology etc using language like Web Ontology Language (OWL) .
The proposal of concluded with the following phrase/prediction: “you are what you think”, which is in the same spirit of René Descartes famous phrase “I think therefore I am” and it can be expressed by the following quote borrowed from . <<In the end, I’ve come to believe in something I call “The Physics of the Quest.” A force in nature governed by laws as real as the laws of gravity. The rule of Quest Physics goes something like this: If you’re brave enough to leave behind everything familiar and comforting, which can be anything from your house to bitter, old resentments, and set out on a truth-seeking journey, either externally or internally, and if you are truly willing to regard everything that happens to you on that journey as a clue and if you accept everyone you meet along the way as a teacher and if you are prepared, most of all, to face and forgive some very difficult realities about yourself, then the truth will not be withheld from you.>>
In a podcast with Joe Rogan, SpaceX chief Elon Musk said "If you assume any rate of improvement at all, games will eventually be indistinguishable from reality" before concluding "that it's most likely we're in a simulation."
Another high-profile proponent to the hypothesis is famous astrophysicist Neil Degrasse Tyson, who said in an NBC news interview that the hypothesis is correct giving "better than 50-50 odds" and adding: 
I wish I could summon a strong argument against it, but I can find none.
Economist Robin Hanson argues a self-interested occupant of a high-fidelity simulation should strive to be entertaining and praiseworthy in order to avoid being turned off or being shunted into a non-conscious low-fidelity part of the simulation. Hanson additionally speculates that someone who is aware that he might be in a simulation might care less about others and live more for today: "your motivation to save for retirement, or to help the poor in Ethiopia, might be muted by realizing that in your simulation, you will never retire and there is no Ethiopia."
A method to test one type of simulation hypothesis was proposed in 2012 in a joint paper by physicists Silas R. Beane from the University of Bonn (now at the University of Washington, Seattle), and Zohreh Davoudi and Martin J. Savage from the University of Washington, Seattle. Under the assumption of finite computational resources, the simulation of the universe would be performed by dividing the continuum space-time into a discrete set of points. In analogy with the mini-simulations that lattice-gauge theorists run today to build up nuclei from the underlying theory of strong interactions (known as quantum chromodynamics), several observational consequences of a grid-like space-time have been studied in their work. Among proposed signatures is an anisotropy in the distribution of ultra-high-energy cosmic rays, that, if observed, would be consistent with the simulation hypothesis according to these physicists. In 2017, Campbell et al. proposed several experiments aimed at testing the simulation hypothesis in their paper "On Testing the Simulation Theory".
In 2019, philosopher Preston Greene suggested that it may be best not to find out if we're living in a simulation since, if it were found to be true, such knowing may end the simulation.
Besides attempting to assess whether the simulation hypothesis is true or false, philosophers have also used it to illustrate other philosophical problems, especially in metaphysics and epistemology. David Chalmers has argued that simulated beings might wonder whether their mental lives are governed by the physics of their environment, when in fact these mental lives are simulated separately (and are thus, in fact, not governed by the simulated physics). Chalmers claims that they might eventually find that their thoughts fail to be physically caused, and argues that this means that Cartesian dualism is not necessarily as problematic of a philosophical view as is commonly supposed, though he does not endorse it. Similar arguments have been made for philosophical views about personal identity that say that you could have been another human being than the one you are, as well as views about qualia that say that colors could have appeared differently than they do (the inverted spectrum scenario). In both cases, the claim is that all this would require is hooking up the mental lives to the simulated physics in a different way.
The first to state the basic concept of reality as a simulation was Plato in 380BCE, in the famous Allegory of the Cave, describing people imprisoned since childhood (but not since birth) led to believe that artificial light-based representations of reality were truly real when, in fact, they were a fabricated illusion.
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.
The laws that we observe just don't look like a competently programmed simulation… They have a lot of hidden complexity. So when you dig deeper you find that there's hidden structure that's not used for anything. Why would you do that, if you're simulating a world? Also the laws are very constrained. They are local; they don't change in time; they don't change in place. In a programmed environment there's no reason to obey any of those constraints… And then there's the embarrassing question of, 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? So it begs the question.
ABSTRACT Observable consequences of the hypothesis that the observed universe is a numerical simulation performed on a cubic space-time lattice or grid are explored. The simulation scenario is first motivated by extrapolating current trends in computational resource requirements for lattice QCD into the future. Using the historical development of lattice gauge theory technology as a guide, we assume that our universe is an early numerical simulation with unimproved Wilson fermion discretization and investigate potentially-observable consequences. Among the observables that are considered are the muon g-2 and the current differences between determinations of alpha, but the most stringent bound on the inverse lattice spacing of the universe, b−1 > ~ 10^11 GeV, is derived from the high-energy cut off of the cosmic ray spectrum. The numerical simulation scenario could reveal itself in the distributions of the highest energy cosmic rays exhibiting a degree of rotational symmetry breaking that reflects the structure of the underlying lattice.