Simulation theory is the idea that the world we experience, including our own minds, could be a computation running on some deeper level of reality. Its modern form is the simulation argument Nick Bostrom published in 2003, which does not claim we are simulated; it argues that one of three possibilities must be true, and one of them is that we almost certainly are. No experiment has found evidence for or against it, which is why most physicists treat it as philosophy rather than settled science.
The question matters because it is older than computers. Whether appearances can be trusted is one of the first questions philosophy ever asked, and simulation theory restates it in the language of the information age. It now shapes how physicists, philosophers and technologists talk about what reality is made of, and it is often confused with neighbouring ideas, above all the holographic principle in physics. The [holographic universe topic hub](/topics/holographic-universe) gathers the site's coverage of that wider conversation.
What is simulation theory?
Simulation theory is a family of claims that our universe, or at least our experience of it, is produced by a computation. Two versions are worth keeping apart. The simulation hypothesis is the direct claim that we live inside a simulation. The simulation argument is Bostrom's more careful reasoning about how likely that is, given some assumptions about technology and minds.
Both rest on an assumption philosophers call substrate independence: the view that a mind depends on the pattern of information processing, not on the material doing the processing. If that is true, a detailed enough computation of a brain would be conscious in the same way a biological brain is. If it is false, a simulation could reproduce the behaviour of people without producing anyone to have an experience, and the argument loses most of its force.
Nick Bostrom's simulation argument
Bostrom's argument is a trilemma: at least one of three statements must be true. His paper "Are You Living in a Computer Simulation?", published in the Philosophical Quarterly in 2003, puts it this way:
- Almost all civilisations at our level of development go extinct before reaching a "posthuman" stage capable of running vast computations.
- Almost no posthuman civilisations are interested in running "ancestor simulations", detailed simulations of their own history.
- We are almost certainly living in a simulation.
The reasoning behind the third option is statistical. If posthuman civilisations exist and run many ancestor simulations, simulated minds would vastly outnumber original, biological ones. If you cannot tell from the inside which kind of mind you are, Bostrom argues, you should assign your credence in proportion to the numbers, a step he calls a bland indifference principle. On those assumptions, the odds favour being simulated.
The point that is most often lost in retellings is that Bostrom did not argue we are in a simulation. He argued that we cannot consistently believe all three of the following at once: that humanity will reach a posthuman stage, that posthumans will run ancestor simulations, and that we are not simulated. Which of the three to drop is left open. An earlier piece on this site, [Of Course We're Living in a Simulation](/of-course-we-re-living-in-a-simulation-an-exploration-of-the-simulation-hypothesis), explores the hypothesis from the believer's side.
Where the idea comes from: from Plato's cave to The Matrix
The intuition behind simulation theory is ancient, even though the computing vocabulary is modern. In Book VII of Plato's Republic, prisoners chained in a cave take the shadows cast on a wall for the whole of reality. In the Zhuangzi, the Daoist philosopher dreams he is a butterfly and, on waking, cannot be sure whether he is Zhuangzi who dreamed of being a butterfly or a butterfly now dreaming of being Zhuangzi. In his Meditations on First Philosophy (1641), René Descartes imagines an evil demon able to deceive him about everything he perceives.
The twentieth century supplied the technical version. Hilary Putnam's "brain in a vat", set out in Reason, Truth and History (1981), asks how anyone could know they were not a brain fed with signals by a computer. On the physics side, the German computer pioneer Konrad Zuse proposed in Rechnender Raum ("Calculating Space", 1969) that the universe might be computed like a cellular automaton, and Edward Fredkin developed similar ideas under the name digital physics. In 1989 the physicist John Wheeler coined the phrase "it from bit", the suggestion that every physical thing derives its existence from information. In the 1990s the roboticist Hans Moravec wrote about minds and whole worlds running as simulations.
Then came The Matrix (1999), which gave the idea its lasting popular image, four years before Bostrom's paper gave it a formal argument. The site's [consciousness topic hub](/topics/consciousness) covers the related question of what a mind is in the first place.
Who takes simulation theory seriously today?
Simulation theory has prominent public advocates, though they differ on what follows from it. At the 2016 Code Conference, Elon Musk said the chance we are living in base reality is "one in billions", reasoning from the rapid improvement of video games. Neil deGrasse Tyson spoke sympathetically of the idea around the same time and has since described himself as more skeptical.
Two books have shaped the recent discussion. Rizwan Virk's The Simulation Hypothesis (2019) approaches the question from video-game design and argues that a simulated world could be built in stages as technology advances. The philosopher David Chalmers, in Reality+ (2022), takes a different line: he argues that even if we are in a simulation, the things we experience are real, built from digital processes rather than from nothing. On his account a simulated table is still a table, which removes much of the sense that simulation theory would make life an illusion.
Can simulation theory be tested?
So far, no test has produced evidence either way, though physicists have proposed ways one might. In 2012 Silas Beane, Zohreh Davoudi and Martin Savage noted that physicists who simulate the strong nuclear force place space on a fine grid, or lattice. If our universe were simulated in a similar way, they suggested, the grid might leave a signature, such as a preferred direction in the highest-energy cosmic rays. No such signature has been found.
A 2017 paper by Zohar Ringel and Dmitry Kovrizhin in Science Advances is often cited as a disproof. It showed that a standard technique for simulating quantum systems on classical computers, quantum Monte Carlo, runs into the "sign problem" for certain systems, making those simulations intractable. That is a genuine result about classical computing, but it says nothing about a simulator with unknown technology and unknown resources, so it does not rule out the simulation hypothesis.
At the other end, the physicist Melvin Vopson proposed in 2023 a "second law of infodynamics", suggesting that information in physical systems tends to be compressed or optimised in a way consistent with a computed universe. The proposal is speculative and has not been accepted by the physics community.
The main objections
The strongest objections target the assumptions, not the arithmetic. The first is testability. The physicist Sabine Hossenfelder has argued that simulation theory, as usually stated, is not a scientific hypothesis: to become one, it would need to show how a simulation reproduces established physics, including quantum field theory, exactly and without leaving detectable errors, and no one has done that.
The second is substrate independence. Whether computation alone produces consciousness is one of the most disputed questions in philosophy of mind, and Bostrom's third option only follows if the answer is yes.
The third is that the argument can undercut itself. The physicist Sean Carroll has pointed out that if simulated worlds can run their own simulations, most observers would sit in the lowest levels, in worlds too limited to simulate anything, yet we appear to be on track to build simulations ourselves. Philosophers have also questioned the reference class: why simulated minds and our own should be counted as the same kind of observer at all.
None of these objections disproves the hypothesis. They explain why most scientists regard it as an open philosophical question rather than a finding.
Simulation theory and the holographic universe are not the same idea
The holographic principle is a result in theoretical physics about where information lives; it says nothing about a computer. Proposed by Gerard 't Hooft in 1993 and developed by Leonard Susskind in 1995, it holds that everything inside a region of space can be described by information on that region's boundary. Juan Maldacena's AdS/CFT correspondence (1997) gave a precise mathematical example of this in a model universe.
Simulation theory, by contrast, is a claim about who or what produces reality. The two are often merged in popular writing because both describe the world in terms of information, but either could be true without the other. The site's explainer [Is the Universe a Hologram?](/is-the-universe-a-hologram-holographic-principle-explained) covers the physics in detail.
Billy Carson's reading
Billy Carson treats reality as a fractal holographic construct in which consciousness is fundamental. In his model, set out in [The Fractal Holographic Universe explained](/the-fractal-holographic-universe-explained-billy-carsons-model-of-reality), the patterns of the cosmos repeat at every scale and each part carries information about the whole. That places his view closer to "the universe is information, or mind" than to "a computer run by aliens": the emphasis falls on consciousness as the ground of reality rather than on a machine behind the screen.
Carson connects this to the Hermetic tradition. The first of the seven principles in The Kybalion (1908), the Principle of Mentalism, states that "The All is Mind; the Universe is Mental", and he reads it as an older expression of the same insight modern simulation language is reaching for. The site's guide to [the Kybalion and the seven Hermetic principles](/the-kybalion-and-the-seven-hermetic-principles-explained) lays out that text on its own terms.
He has explored the question at length on the 4biddenknowledge Podcast. In the episode Could We Be Living in a Simulation? he sets out the case in his own words, and Did the Anunnaki Program the Matrix? takes it into his reading of ancient texts, alongside fractal reality and the idea of soul traps. These are his interpretations. Mainstream physics and philosophy do not treat consciousness as established as fundamental, and they do not link simulation theory to Sumerian sources; readers can weigh his synthesis against the scholarship summarised above.
Watch, read and go deeper
Billy Carson's own series on 4BK TV, [Billy Carson 4biddenknowledge](/watch/billy-carson-4biddenknowledge-podcast), carries his talks on consciousness, reality and ancient knowledge. For the audio version, start with the podcast episode Could We Be Living in a Simulation?. His book Fractal Holographic Universe develops the model summarised in his reading above. The [holographic universe topic hub](/topics/holographic-universe) brings the physics, the philosophy and his interpretation together in one place.
Frequently asked questions
Who came up with simulation theory?
The formal simulation argument comes from the philosopher Nick Bostrom, in his 2003 paper "Are You Living in a Computer Simulation?" in the Philosophical Quarterly. The underlying doubt about whether perception can be trusted is much older, running from Plato's cave and the Zhuangzi through Descartes and Hilary Putnam's brain in a vat.
Is there any evidence we are living in a simulation?
No direct evidence has been found. The best-known proposed test, a 2012 suggestion by Beane, Davoudi and Savage to look for grid-like signatures in high-energy cosmic rays, has turned up nothing. The absence of evidence does not rule the idea out, which is why it remains an open question.
Did physicists prove we are not in a simulation?
No. A 2017 paper by Ringel and Kovrizhin showed that certain quantum systems cannot be efficiently simulated on classical computers using quantum Monte Carlo methods. News coverage presented this as a disproof, but it only limits one kind of classical computation and says nothing about a simulator whose technology is unknown.
Is simulation theory the same as the holographic principle?
No. The holographic principle, from 't Hooft, Susskind and Maldacena, is a result in quantum gravity about information being encoded on a boundary. Simulation theory is a claim that reality is produced by a computation. Both use the language of information, but neither implies the other.
What does Billy Carson believe about simulation theory?
Billy Carson describes reality as a fractal holographic construct in which consciousness is fundamental, which he connects to the Hermetic principle that the universe is mental. His view emphasises mind and information rather than a literal computer, and he presents it as his interpretation of ancient texts and modern physics.
Sources and further reading
- Nick Bostrom, "Are You Living in a Computer Simulation?", Philosophical Quarterly (2003)
- René Descartes, Meditations on First Philosophy (1641)
- Hilary Putnam, Reason, Truth and History (1981)
- Silas R. Beane, Zohreh Davoudi and Martin J. Savage, "Constraints on the Universe as a Numerical Simulation" (2012)
- Zohar Ringel and Dmitry L. Kovrizhin, "Quantized gravitational responses, the sign problem, and quantum complexity", Science Advances (2017)
- Rizwan Virk, The Simulation Hypothesis (2019)
- David J. Chalmers, Reality+: Virtual Worlds and the Problems of Philosophy (2022)
- Leonard Susskind, "The World as a Hologram", Journal of Mathematical Physics (1995)
