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Simulated reality is the hypothesis that reality could be simulated—for example by quantum computer simulation—to a degree indistinguishable from "true" reality. It could contain conscious minds which may or may not be fully aware that they are living inside a simulation. This is quite different from the current, technologically achievable concept of virtual reality. Virtual reality is easily distinguished from the experience of actuality; participants are never in doubt about the nature of what they experience. Simulated reality, by contrast, would be hard or impossible to separate from "true" reality. There has been much debate over this topic, ranging from philosophical discourse to practical applications in computing.
A version of the simulation hypothesis was first theorised as a part of a philosophical argument on the part of René Descartes, and later by Hans Moravec. The philosopher Nick Bostrom developed an expanded argument examining the probability of our reality being a simulation. His argument states that at least one of the following statements is very likely to be true:
- 1. Human civilization or a comparable civilization is unlikely to reach a level of technological maturity capable of producing simulated realities or such simulations are physically impossible to construct.
- 2. A comparable civilization reaching aforementioned technological status will likely not produce a significant number of simulated realities (one that might push the probable existence of digital entities beyond the probable number of "real" entities in a Universe) for any of a number of reasons, such as diversion of computational processing power for other tasks, ethical considerations of holding entities captive in simulated realities, etc.
- 3. Any entities with our general set of experiences are almost certainly living in a simulation.
- 4. We are living in a reality in which posthumans have not developed yet and we are actually living in reality.
Bostrom's argument rests on the premise that given sufficiently advanced technology, it is possible to represent the populated surface of the Earth without recourse to digital physics; that the qualia experienced by a simulated consciousness are comparable or equivalent to those of a naturally occurring human consciousness, and that one or more levels of simulation within simulations would be feasible given only a modest expenditure of computational resources in the real world.
If one assumes first that humans will not be destroyed nor destroy themselves before developing such a technology, and that human descendants will have no overriding legal restrictions or moral compunctions against simulating biospheres or their own historical biosphere, then, Bostrom argues, it would be unreasonable to count ourselves among the small minority of genuine organisms who, sooner or later, will be vastly outnumbered by artificial simulations.
Epistemologically, it is not impossible to tell whether we are living in a simulation. For example, Bostrom suggests that a window could pop up saying: "You are living in a simulation. Click here for more information." However, imperfections in a simulated environment might be difficult for the native inhabitants to identify and for purposes of authenticity, even the simulated memory of a blatant revelation might be purged programmatically. Nonetheless, should any evidence come to light, either for or against the skeptical hypothesis, it would radically alter the aforementioned probability.
Computationalism is a philosophy of mind theory stating that cognition is a form of computation. It is relevant to the Simulation hypothesis in that it illustrates how a simulation could contain conscious subjects, as required by a "virtual people" simulation. For example, it is well known that physical systems can be simulated to some degree of accuracy. If computationalism is correct and if there is no problem in generating artificial consciousness or cognition, it would establish the theoretical possibility of a simulated reality. Nevertheless, the relationship between cognition and phenomenal qualia of consciousness is disputed. It is possible that consciousness requires a vital substrate that a computer cannot provide and that simulated people, while behaving appropriately, would be philosophical zombies. This would undermine Nick Bostrom's simulation argument; we cannot be a simulated consciousness, if consciousness, as we know it, cannot be simulated. The skeptical hypothesis remains intact, however, and we could still be envatted brains, existing as conscious beings within a simulated environment, even if consciousness cannot be simulated. It has been suggested that whereas virtual reality would enable a participant to experience only three senses (sight, sound and optionally smell), simulated reality would enable all five (including taste and touch).
Some theorists have argued that if the "consciousness-is-computation" version of computationalism and mathematical realism (or radical mathematical Platonism) are true then consciousnesses is computation, which in principle is platform independent and thus admits of simulation. This argument states that a "Platonic realm" or ultimate ensemble would contain every algorithm, including those which implement consciousness. Hans Moravec has explored the simulation hypothesis and has argued for a kind of mathematical Platonism according to which every object (including, for example, a stone) can be regarded as implementing every possible computation.
A dream could be considered a type of simulation capable of fooling someone who is asleep. As a result, the "dream hypothesis" cannot be ruled out, although it has been argued that common sense and considerations of simplicity rule against it. One of the first philosophers to question the distinction between reality and dreams was Zhuangzi, a Chinese philosopher from the 4th century BC. He phrased the problem as the well-known "Butterfly Dream," which went as follows:
Once Zhuangzi dreamt he was a butterfly, a butterfly flitting and fluttering around, happy with himself and doing as he pleased. He didn't know he was Zhuangzi. Suddenly he woke up and there he was, solid and unmistakable Zhuangzi. But he didn't know if he was Zhuangzi who had dreamt he was a butterfly or a butterfly dreaming he was Zhuangzi. Between Zhuangzi and a butterfly there must be some distinction! This is called the Transformation of Things. (2, tr. Burton Watson 1968:49)
The philosophical underpinnings of this argument are also brought up by Descartes, who was one of the first Western philosophers to do so. In Meditations on First Philosophy, he states "... there are no certain indications by which we may clearly distinguish wakefulness from sleep", and goes on to conclude that "It is possible that I am dreaming right now and that all of my perceptions are false".
Chalmers (2003) discusses the dream hypothesis and notes that this comes in two distinct forms:
- that he is currently dreaming, in which case many of his beliefs about the world are incorrect;
- that he has always been dreaming, in which case the objects he perceives actually exist, albeit in his imagination.
Both the dream argument and the simulation hypothesis can be regarded as skeptical hypotheses; however in raising these doubts, just as Descartes noted that his own thinking led him to be convinced of his own existence, the existence of the argument itself is testament to the possibility of its own truth. Another state of mind in which some argue an individual's perceptions have no physical basis in the real world is called psychosis though psychosis may have a physical basis in the real world and explanations vary.
The existence of simulated reality is unprovable in any concrete sense: any "evidence" that is directly observed could be another simulation itself. In other words, there is an infinite regress problem with the argument. Even if we are a simulated reality, there is no way to be sure the beings running the simulation are not themselves a simulation and the operators of that simulation are not a simulation.
"Recursive simulation involves a simulation or an entity in the simulation, creating another instance of the same simulation, running it and using its results" (Pooch and Sullivan 2000).
Other uses of the simulation hypothesis in philosophy
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). They might eventually find that their thoughts fail to be physically caused. Chalmers 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.
Similarly, Vincent Conitzer has used the following computer simulation scenarios to illuminate further facts—facts that do not follow logically from the physical facts—about qualia (what it is like to have specific experiences), indexicality (what time it is now and who I am), and personal identity. Imagine a person in the real world who is observing a simulated world on a screen, from the perspective of one of the simulated agents in it. (This is not the kind of simulated reality that is the topic of this article, but we will get to such a simulated reality in the next step of the argument.) The person observing knows that besides the code responsible for the physics of the simulation, there must be additional code that determines in which colors the simulation is displayed on the screen, and which agent's perspective is displayed. (These questions are related to the inverted spectrum scenario and whether there are further facts about personal identity.) That is, the person can conclude that the facts about the physics of the simulation (which are completely captured by the code governing the physics) do not fully determine her experience by themselves. But then, Conitzer argues, imagine someone who has become so engrossed in the simulation that she has forgotten that it is a simulation she is watching. For this to be the case, the simulation needs to have an exceptionally high fidelity, bringing us into the territory of simulated reality. (This situation also resembles the one in the dream argument discussed above.) In this case, could she not still reach the same conclusion that the facts about the physics (of the simulated reality, though she does not realize it is simulated) do not fully determine her experience by themselves? And if so, can we not conclude the same in our own daily lives?
Simulated reality in fiction has been explored by many authors, game designers and film directors.
- Artificial life
- Artificial society
- Augmented reality
- Boltzmann brain
- Computational sociology
- Consensus reality
- Digital philosophy
- Digital physics
- Margolus–Levitin theorem
- Mind uploading
- OpenWorm, project to simulate the roundworm Caenorhabditis elegans.
- Philosophy of information
- Simulation hypothesis
- Social simulation
- Theory of knowledge
- Tipler's "Omega point"
- Virtual reality simulator
- Virtual worlds
Major contributing thinkers
- Nick Bostrom and his simulation argument
- René Descartes (1596–1650) and his Evil Demon, sometimes also called his 'Evil Genius'
- George Berkeley (1685–1753) and his "immaterialism" (later referred to as subjective idealism by others)
- Plato (424/423 BC – 348/347 BC) and his Allegory of the Cave
- Zhuangzi (around the 4th century BCE) and his Chinese Butterfly Dream
- Moravec, Hans, Simulation, Consciousness, Existence
- Moravec, Hans, Platt, Charles Superhumanism
- Moravec, Hans Pigs in Cyberspace
- Bostrom, Nick (2003). "Are You Living in a Computer Simulation?". Philosophical Quarterly. 53 (211): 243–255.
- Bruno Marchal
- Russel Standish
- Hut, P.; Alford, M.; Tegmark, M. (2006). "On Math, Matter and Mind". Foundations of Physics. 36 (6): 765–794. arXiv:physics/0510188. Bibcode:2006FoPh...36..765H. doi:10.1007/s10701-006-9048-x.
- "There is no logical impossibility in the supposition that the whole of life is a dream, in which we ourselves create all the objects that come before us. But although this is not logically impossible, there is no reason whatever to suppose that it is true; and it is, in fact, a less simple hypothesis, viewed as a means of accounting for the facts of our own life, than the common-sense hypothesis that there really are objects independent of us, whose action on us causes our sensations." Bertrand Russell, The Problems of Philosophy
- René Descartes, Meditations on the First Philosophy, from Descartes, The Philosophical Works of Descartes, trans. Elizabeth S. Haldane and G.R.T. Ross (Cambridge: Cambridge University Press, 1911 – reprinted with corrections 1931), Volume I, 145-46.
- Chalmers, J., The Matrix as Metaphysics, Department of Philosophy, University of Arizona
- Valberg, J.J. (2007). Dream, Death, and the Self. Princeton University Press. ISBN 9780691128597.
- Bostrom, Nick (2009). "The Simulation Argument: Some Explanations" (PDF).
If each first-level ancestor-simulation run by the non-Sims requires more resources (because they contain within themselves additional second-level ancestor-simulations run by the Sims), the non-Sims might well respond by producing fewer first-level ancestor-simulations. Conversely, the cheaper it is for the non-Sims to run a simulation, the more simulations they may run. It is therefore unclear whether the total number of ancestor-simulations would be greater if Sims run ancestor-simulations than if they do not.
- Pooch, U.W.; Sullivan, F.J. (2000). Recursive simulation to aid models of decisionmaking. Simulation Conference. 1 (Winter ed.). p. 958. doi:10.1109/WSC.2000.899898. ISBN 978-0-7803-6579-7.
- Chalmers, David (January 1990). "How Cartesian Dualism Might Have Been True".
- Conitzer, Vincent (2018). "A Puzzle about Further Facts". Erkenntnis. arXiv:1802.01161. doi:10.1007/s10670-018-9979-6.
- Chalmers, David (2005). "The Matrix as Metaphysics". In C. Grau. Philosophers Explore the Matrix. Oxford University Press. pp. 157–158. ISBN 9780195181067. LCCN 2004059977.
Evil Genius Hypothesis: I have a disembodied mind and an evil genius is feeding me sensory inputs to give the appearance of an external world. This is René Descartes’s classical skeptical hypothesis... Dream Hypothesis: I am now and have always been dreaming. Descartes raised the question: how do you know that you are not currently dreaming? Morpheus raises a similar question: 'Have you ever had a dream, Neo, that you were so sure was real. What if you were unable to wake from that dream? How would you know the difference between the dream world and the real world?'... I think this case is analogous to the Evil Genius Hypothesis: it's just that the role of the “evil genius” is played by a part of my own cognitive system! If my dream-generating system simulates all of space-time, we have something like the original Matrix Hypothesis.p.22
- Copleston, Frederick (1993) . "XIX Theory of Knowledge". A History of Philosophy, Volume I: Greece and Rome. New York: Image Books (Doubleday). p. 160. ISBN 978-0-385-46843-5.
- Copleston, Frederick (1994) . "II Descartes (I)". A History of Philosophy, Volume IV: Modern Philosophy. New York: Image Books (Doubleday). p. 86. ISBN 978-0-385-47041-4.
- Deutsch, David (1997). The Fabric of Reality. London: Penguin Science (Allen Lane). ISBN 978-0-14-014690-5.
- Lloyd, Seth (2006). Programming the Universe: A Quantum Computer Scientist Takes On the Cosmos. Knopf. ISBN 978-1-4000-4092-6.
- Tipler, Frank (1994). The Physics of Immortality. Doubleday. ISBN 978-0-385-46799-5.
- Lem, Stanislaw (1964). Summa Technologiae. ISBN 978-3-518-37178-7.