On the question of the simulation hypothesis (i.e. that reality is a simulation), a friend of mine once remarked he didn't accept it on the grounds of Ockham's razor. To me (with my admittedly instrumentalist view of science) this seems a misuse of Ockham's razor in that all my friend is really claiming is that it isn't empirically necessary (and hence outside of science).

Is the simulation hypothesis outside of science? If so, then does it pose a problem for scientific realism? If not, is it falsifiable? Is it an empirical question?


6 Answers 6


I'm not sure that being in a simulated universe really poses a significant question for scientists. On my reading this is still essentially a metaphysical question. The realism-idealism debate hasn't stopped any scientists from getting to work that I know of -- meta is ultimately a distraction, at least in the last instance, and engineers and scientists have things to build and problems to solve (not years to worry about whether we're in a simulated universe or not and how you'd even know the difference.)

In fact, you'll probably find that most philosophers generally don't spend a lot of time in their formal expositions worrying over these sorts of things either -- they too have more interesting fish to fry.

That said, I am currently working through De Landa's Philosophy and Simulation, which I highly recommended for a thoughtful (and non-Bostrom-oriented approach) to some of the larger questions of emergence and simulation and their implications for philosophy and science.

Now, if we are granting that we are in someone's ancestor simulation, it is certainly possible that we may run into certain limits "hardcoded" by various parameters of the simulation -- an example might be that there could be clauses in the simulation programming designed to identify civilizations that begin to develop the ability to simulate, and take some in-simulation action based on those events (which could include just about anything up to and including triggering the termination of the simulation, etc.)

The simulation hypothesis is in a way very similar to the claim the universe has a creator, and unless these sorts of "external context" claims end up incorporated into a societal effort to repress innovation, these sorts of ideas certainly don't stop scientists and engineers from solving problems and building useful new things.

UPDATE: I have realized your question is somewhat more nuanced than my initial reading suggested.

I might suggest that Ockham's razor cuts both ways on these sorts of questions. Remember that Bostrom's own presentation of the question is a trilemma: either

  1. the fraction of human-level civilizations that reach a posthuman stage is very close to zero;
  2. the fraction of posthuman civilizations that are interested in running ancestor-simulations 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

Ockham's Razor would initially indeed seem to suggest that the simulation hypothesis 'requires less assumptions'; however given the degree of unknowability here it would seem as difficult to assert this unqualifiedly as it is to imagine a scientific experiment which could validate the principle. In my opinion it's at least apparently unfalsifiable, though as I have suggested above, hypothetically we might run into certain limits imposed by the simulator on the simulation.

My sense of the hypothesis is that basically it isn't falsifiable or empirical; there is an analytic dimension to Bostrom's analysis here that simply can't be validated in any experimental way. Hence I don't think it poses a significant problem for scientific realism.

Finally, it may help to recall Bostrom's own conclusion:

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 relatively wealthy 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'm also thinking of an omphalos-type situation where a simulation has been running for, say, 5 days of in-world time but empirically the world appears billions of years old. If an instrumentalist came to the belief she was in a 5-day-old simulation, she could still accept the billions-year-old model (as still the best predictor of future observations within the world even though ultimately not true). But how would a scientific realist coming to that belief react? Commented Jun 20, 2011 at 23:21
  • 1
    Primal screaming?
    – Joseph Weissman
    Commented Jun 20, 2011 at 23:22
  • @James, a properly nuanced scientific realism would be able to incorporate the simulation hypothesis as soon as it became falsifiable -- i.e., if it were demonstrated scientifically that we were in a simulation. As it stands it is just a conjecture. (Also -- just to avoid extended comment-based discussion -- you are welcome to bug me in chat.)
    – Joseph Weissman
    Commented Jun 20, 2011 at 23:32

It seems that reality, simulated or not, consists of some currency (eg, matter/energy) and is governed by laws. Using science, we have the ability to observe/quantify the present state of reality, and also thereby to infer the laws according to which reality changes. Given such information, I can think of two scenarios that a person might take as evidence that there is a system outside of (or encapsulating) reality: contravention of the laws of reality--especially a change that manifests in a highly complex way (direct manipulation of complex systems rather than of base systems)--or improbability of the present state of reality, given the laws of reality.

See that both of those arguments rest on probability. They are paralleled in philosophy of religion by, respectively, the argument from miracles and the teleological argument. Also, it can be seen that the simulation hypothesis overlaps (at least partially) with the god (sentient, omnipotent, omni-etc. creator) hypothesis in that both propose accounts of reality wherein a sentient being outside of, or in a realm encapsulating, our own reality is responsible for creating, and defining the outcome/behavior of, our reality. Thus the discourse relating to those aspects of philosophy of religion, and whether they can form a basis for scientifically testing the existence of a creator, also applies to the simulation hypothesis.

An obvious problem here is the fallibility and never-guaranteed completeness of empirical findings/models. How can you tell if something is improbable given, or violates, the laws of reality, if you cannot be sure of (or, as at present, are sure of your ignorance of) those laws. Was that (for example) spontaneous resurrection truly a miracle (assuming it happened at all), or was it perhaps caused by the unknown presence of complex systems within our reality? That thread of contemplation leads one to ask whether final (total and complete) reduction of physics to its most base elements will (i.e. does) lead to a mathematical understanding that, at least given faith in mathematics, is the basis for being confident that the model is complete and correct. In other words, could we derive a set of laws that fully describe reality, and in a such way that a mathematically simpler basis for reality is provably not possible (e.g. if we found out that physics results ultimately from the simplest kind of cellular automata that is capable of leading to those laws, or to such complexity). If physics does reduce to such a mathematical understanding, then there is a viable (but yet not achieved) basis for using observation of reality's present state as evidence bearing on the question of simulation.

But certainty is not the only roadblock here. For example, because of the multiple worlds hypothesis (and probably other reasons), the teleological argument fails to lead to conclusions regarding sentient intervention, even when the present state of reality (traditionally, the teleological argument considers the presently known laws of physics as part of what is improbable [along with the material composition of the universe, and sometimes the outcome], but here we can reduce that and hypothesize that those laws are actually the outcome [thus constituting part of 'the present state of reality'] of the unknown and more-base actual laws) is improbable given its laws. Of course, since we do not yet know the laws of our reality, we may propose simulation scenarios that lead to hypotheses regarding what we would expect those laws to be, and if those hypotheses are supported (or at least not refuted) by our future findings regarding the laws, then we could have scientific evidence that reality is a simulation. However, it is important here that each scenario in question leads to unique predictions; predictions that would not be entailed by any other (or at least any non-simulation) scenarios. Its worth noting here that, of course, proof against the improbability of the present state of reality does not constitute evidence against the simulation hypothesis.

The argument from miracles is seemingly more useful. If only a single miracle of the complex variety occurs, we may recognize the possibility that, in some catalog of infinite realities, some realities had to experience that sole miracle that 'defies' probability. If, however, we witness multiple miracles of the complex variety, then we can be very confident that something 'sentient' (or at least complex) exists outside our reality and is capable of influencing our reality. The question then is one of interpreting the meaning of miraculous influence: if something exists outside our reality, is its relationship one of being the substrate or genesis of our reality, or is it simply an independent entity capable, for some reason, of interaction--and does that interaction simply imply a further set of laws (laws of our reality) that govern interactions with other realities. If a reality can reach a state whereby, by virtue of the (potentially deliberate) actions of internal sentient/complex system(s), its interactions with another entity can be governed, and are governed towards the goal of influencing the outcome (state) of the other reality, how does this relate to the idea of a simulated reality?

It seems the gut human instinct is to relate worlds or universes using spatial metaphors, but space is a troubling concept even within our reality, and should probably not be recruited in reasoning about the relations between realities, worlds, universes, or whatever you want to call them. However, the relationship can be defined in other ways: does reality X influence reality Y and vice-verse? Does either influence contravene the laws of the influenced reality? Does either reality have direct access to information about the other (access that does not come from an interaction; access that does not necessarily or automatically influence the observed system during the process of observation.) Note that these refer (or at least relate) to the concepts of omnipotence and omniscience.

Ultimately, scientifically tackling the simulation hypothesis involves making testable predictions. This is complicated, for one, by the number of possible variations on the concept. If we are considering scenarios of a sentient progenitor(s) who deliberately created the simulation, then things are also complicated by issues of motive/intention and capability/knowledge. The question of motive may parallel theoretical work regarding the motives (and evolution thereof) of future AI. Substrate is potentially a factor under any scenario, though may be conceptually/metaphysically indistinguishable (at least if considering only from our side) from the laws of reality.

  • This account of miracles seems to take no account of Hume's criticisms of them
    – CriglCragl
    Commented Aug 26, 2018 at 1:16

The simulation hypothesis seems to be the foundation of science itself: by examining phenomena (that are all transient, everchanging, non-permanent and therefore temporary) we attempt to derive a conclusion about the "true nature of things." This naturally falls apart when you observe that it is possible that there are no things.

On the grounds of Ockham's Razor, one is tempted to agree with your friend because even the assumption that we are conscious and able to philosophize (for lack of a better term) is quite a stretch. Truly, if all conscious beings were able to observe reality from a standpoint so clear and tranquil that there was no perception of "time" then there would be no perception of "logic" or "reason" and subsequently no perception of a "simulation."

How is it possible to perceive the absence of time? If you consider that all action is momentary and fleeting, and -- as the Buddhists would say -- relinquish attachment to anything but the present moment, you begin to dwell in an awareness that is outside the scope of the simulation hypothesis.

To answer your question,

is it outside the scope of science? Most definitely. Science is based on observable phenomenon, and it would be impossible to "view from outside" that which is only measurable (and only exists, so-to-speak) from within.

does it pose a problem for scientific realism? No. It is like suggesting that sweetness is a problem of sugar. They are inextricable traits from the point of view of the observer.

is it an empirical question? In my understanding, empirical implies that we can measure and use alternative forms of matter to label/identify/communicate/ and express a meaning or quantity -- is it possible to measure the vastness of the ocean as a fish? Really, one takes for granted the assumption that there is some physical, unchanging "root" of things to which perception can hold on to. Notice that everything changes, that nothing stays the same, and that sentience typically clings to that which it believes to feel good and avoids that which it believes to feel bad. To say that the simulation has an inherent existence is to confuse the will and desire to avoid pain and pleasure with the "will" of the environment. Truly, they are separate. Yet, they are also one -- thanks to the "bridge of perception" if you will.

What negative consequence does the idea of a simulation imply, exactly? A simulation is simply a false, transparent cover of something. Whether this is "good" or "bad" is up to interpretation by you. Really, the word "simulation" is just a label. It describes not the true nature of reality because the layer you are trying to talk about is far "below" the layer of words and description. This sentence is really part of the harmonious and rhythmic breathing of the universe -- "information" is continuous. What is "observed" is not the frames, but the "movie" that exists as we cling to the familiar, on both conscious and subconscious levels. Really, the film is a series of frames that exchange places. If you were to study one frame, you would see a static picture. If you were to watch the movie, you enjoy a continuous stream of slightly-changing phenomena, such that you can perceive and understand a story, a plot, an emotion or feeling.

Really, perception is the most basal tie we humans have to understanding the true nature of things. Perhaps, instead of asking "is this a simulation?" one might find more wisdom in pondering "what is a simulation?" Truly, you will only be satisfied with an answer once you have had the internal insight of wisdom and understanding. To communicate my view is simply to hope that it stirs your subconscious into curiosity about that which is often observed-as-totality.

Love and Wisdom :)


Simulation Hypothesis is already part of science. Quantum mechanics scientists produced a paper in 2017 to test the double slit experiment in a new way specifically to try to prove or disprove Simulation Hypothesis.

Here is CalTech's paper about the test: http://users.cms.caltech.edu/~owhadi/index_htm_files/IJQF2017.pdf


The simulation hypothesis is firmly outside of science, but it has some implications science can be interested in. Science is concerned with empirical facts and building models from that. The simulation hypothesis asserts that all empirical facts are not real, and that in fact everything is a simulation. Such a statement must, by necessity be outside of empiricism, thus outside of science.

However, the simulation hypothesis does interact with science as a source of possibilities. Science is moved forward by tests which reveal new empirical data, and our search for new empirical data is indeed subject to the bounds of our own imaginations. The simulation hypothesis suggests a lot of places to look for where the universal simulation might "cheat" (I'd say "lower fidelity" over "cheating," but "cheat" isn't too far off). This can lead science to go gather empirical data in directions that might otherwise not have been explored. We can look in the directions we take our simulations and ask "does the universe take the same shortcuts?"

Of course, should they find something, it would not be "artifacts proving we are in a simulation." Rather it would merely be evidence that the universe is more weird than we ever thought it was. The universe has a remarkable track record of proving as such, so yet another proof would not be out of the norm.


The simulation hypothesis (SH) is false and also empirically untestable. The theory of computation explains that any physical system can be simulated by a universal computer, including any computer:


So if the SH is true it will be impossible for us to learn anything about the hardware running the simulation. This means that the SH is untestable. The SH that it is impossible for us to understand how the world works because we can't understand anything about how the real world works: that is, we can't know anything about the simulator. The SH is also incapable of explaining anything about how the world works because we can't know anything about the hardware and so no feature of how the world we see around us can be explained by that hardware.

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