Readers reply: how do we know we’re not living in a simulation like the Matrix?

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How do we know we’re not living in a simulation like the Matrix? Jack Freedom, Bristol

Send new questions to nq@theguardian.com.

Readers reply

Isn’t this just the kind of article our biomechanical overlords would simulate in order to keep us compliant in our pods? kingsize

I took the red pill and nothing materially changed other than a rash that I had had for a week or so cleared up. OfficerKrupke

Not ruling it out, but if we were living in software, it is the most reliable software ever because there never seem to be any disruptive updates. Liam Collins

The idea that we may be living in a matrix-like universe is called the simulation theory, and was first proposed by Nick Bostrom. It argues that human technology is advancing at such a rate that in the future we will have the ability to simulate entire universes filled with details as rich and beautifully complex as our own. These simulated universes would also contain beings that were genuinely conscious as a result of the advanced ability of the simulation, and so would be able to think and would be self-aware in the same way that we can and do. These beings could be indistinguishable from us in terms of the depth of their minds, the only difference being that their life springs from circuit boards and artificial design rather than the real world which has given life to us. These beings then being no less able or imaginative than us would progress to a point of technological advancement at which they could create and run their own simulations. The simulated minds they create may do likewise, and so there could be simulations inside of simulations. There could be billions of universes therefore being simulated in a chain with only one base reality (the “real” world) at the start. That being the case, it looks far more likely that any one individual would be living in a simulated universe, rather than the real one. Once we acknowledge this possibility, we have to then consider that these odds apply to us as well, and so according to the theory presented we are far more likely to be living in a simulation than the real world.

One counter-argument is to consider that all of these simulations have a common feature: they all have their own simulation. The only universes that might not are the most recent simulated universe – as its inhabitants may not have yet developed the technology necessary to create one – or base reality, if it turns out that simulated universes aren’t possible. That brings our odds to at least 50/50, which is preferable to the billion-to-one conclusion reached above. Unfortunately, this line of reasoning assumes that each universe can only create one simulation, which isn’t necessarily the case. Each node on the chain of simulated universes could have many branches, each with a simulation on the end, bringing our probability back to a billion to one. Benjamin Dixon

What I always found interesting about Bostrom’s idea are the ethics that emerge from this assumption. Basically, we should treat any simulated realities with dignity and respect because if we don’t we increase the likelihood that consciousnesses in “higher” reality than ours will mess around with us. I feel much worse about how I treated my Sims now … ajukes2k

You may be interested in David Kipping’s paper A Bayesian Approach to the Simulation Argument. Much more maths than in Bostrom’s original paper, but nothing fiercer than conditional probability and Bayes’ theorem, plus the ability to sum a geometric series, is required. As you would expect, there is a good reference list to the literature too. FinrodFelagund

Michio Kaku has an answer to this – basically because the smallest size of “computer” needed to run a simulation of the universe is … the universe, it’s more logical that we are not living in a simulation. I rather like the idea, though, not least because it offers the small chance of an “afterlife” for the non-religious. ChestnutSlug

Not sure that’s true, though. All that’s needed is to run something that looks like the universe from where you (or I) sit. You might think there’s an awfully big universe out there, but if you only look at it in terms of images on a screen, then all you need is enough power to colour the screen. I quite like the idea that a simulation explains quantum uncertainty: a state doesn’t exist until it’s been observed: it’s uncertain because it hasn’t yet been computed in the simulation … No, of course I don’t believe any of that. It’s fun trying, though. conejo

Some make a pretty plausible case: see Rizwan Virk’s The Simulation Hypothesis and a recent article in Scientific American. Madeleine Bowman

In a sense we definitely are living in a simulation, since what we experience is coloured by our own subjective experience and judgment, expectations, our own programming. How we perceive “reality” may well not be particularly real. Equally, what we are fed, plus groupthink, societal “norms” and expectations, biases etc, can take us a very long way from being able to objectively perceive what is actually happening. We are a walking Matrix. It’s virtually impossible to step outside your own normal and become embedded in any kind of physical reality. You only have to look at other societies around the world and how insane they look to realise that. LorLala

We are living in a simulation, but not in the way you might think. In his Republic, Plato suggests that something can be tangible and unreal, if it purports to be something it is not (as, for example, a statue does). As I look out of my window in 2021 England, I see toytown cars styled to look friendly or aggressive, driving past toytown newbuild houses designed to evoke fake nostalgia, inhabited by disoriented people who vote for toytown politicians and watch surgically enhanced bimbos on so-called reality TV. They are firmly in the Matrix, albeit a tangible Matrix, and the perennial sigh of their oppressed nature is “O God, please protect me from everything that is really real”. I’m sorry, but you did ask. PaulSecret

The state of the current government suggests that if not a simulation we may indeed be living in some bleak dark comedy. DougieGee

There is one piece of evidence that we do indeed live in a computer simulation. Computer simulations are essentially bits of data, which is then presented to the observer, or subject in our case, as objects. The data will contain all the information necessary to present and animate the object, including physical and psychological characteristics. But if the data gets corrupted, then the representation will change unexpectedly. And if the data goes missing, or is corrupted so badly that it cannot be represented, then the object will disappear.

Which brings me to my one piece of evidence. How many of us have experienced the inexplicable disappearance of a sock? Yes, folks, odd socks are the irrefutable piece of evidence that we do live in a simulation – and a sloppy one at that … vishnoo

I’d like to think that a simulated world would be free of pandemics, Brexits, racists, uber-capitalists, tabloid journalism, super-leagues, sausage bans, hives, bad smells, etc – surely our Matrix Overlords would want to keep us feeling complacently sedate and safe, no? Unless, of course, they had a sadistic streak and a perverse sense of humour … AmadanDubh

Have you never played SimCity? At least half the fun is in dealing with disasters. saganIsMyHomeboy

This is an epistemic question. Epistemology is concerned with the beliefs we hold and our justification for holding them. I think the lesson to learn from this question is that we can never be sure we know anything, and we should be constantly evaluating our beliefs and what we know in light of new experience, as it is difficult to prove we know anything. Cauvghn

Philosophers have spent an absurd amount of time attempting to answer this question. It is easy to get bogged down in the details of their numerous theories of knowledge, which typically (though not invariably) seek to establish that we do know that we’re not living in a simulation. But all those theories don’t change a fundamental point: everything would appear to us exactly the same if we are in a (perfect) simulation and if we are not. As a result, there will always be some reason to doubt that things are as they appear. Paul Dimmock

The Middle East, The Kardashians, racism and sexism, homophobia and Trump are all human conditions that a machine could never attain the sufficient level of advanced stupidity to mimic. Jeremy Jones

We are living in a simulation that we create with our own minds. Pavlin Petkov

I believe simulation theory and our current understanding of physics are incompatible. Why?

First, if everything in the simulation is captured within one framework of true determinism, the processing power required for modelling all the trajectories of the units of the (visible) universe would in fact, due to power laws, implode our own universe – even when some of these trajectories and interactions are constrained by universal rules (eg max velocity at speed of light). And yes, this applies even when the simulation is run via quantum computing (where we assume near perfect energy efficiency). In line with the mass-energy equivalence law, E=mc2, information processing = energy = mass. Then, for simulation theory to still work out, there needs to be an external source of mass/energy, far greater than the universe simulated, to supply the processing power to simulate our universe. This simulation therefore needs to physically take place in a different and far greater entity than our own visible universe. So: if simulation operates within a framework of true determinism, processing power required for that single simulation we are all in would far exceed that which is embodied by the mass of our known universe. The simulated universe would implode in on itself or requires a significant supply from an external entity entirely.

Now, if we want to look beyond this processing-power limitation in the case of true determinism, a simulation of our universe would require a significant degree of random laws dictating trajectories of the simulated agents (whatever their unit may be) and their interactions (leading to a far smaller parameter space, which relieves, to some extent, from the power laws that determinism needs to deal with). Computer science has yet to find a way for generating true randomness, but for argument’s sake, let’s assume this limitation has long been overcome by those superior beings running the simulation of our universe. Then still, by virtue of lack of complete determinism, no simulation would be the same; no valuable patterns can be extracted from each simulation alone. This would mean that multiple (read: infinitely many) simulations would need to be run in parallel in order to be valuable, implying that, without determinism, simulation theory would go hand in hand with infinitely many parallel “universes”. This again lands us at the issue of processing power required, which would be so enormous that it seems to defeat the purpose. Whatever that may be (perhaps this is the true psychological conundrum with simulation theory). Naomi Iris van den Berg

When I first watched The Matrix, I had to leave the room when it got to the point of the choice between the red pill and the blue pill, and chose to watch the microwave oven instead … It was too plausible and I couldn’t decide which one to take. Being a diagnosed schizophrenic probably plays a role here, but I also receive enough synchronicity and precognition to keep me guessing as to the possibility of a holographic universe. It would explain a lot. There is a theory along these lines in modern quantum physics and I’ve seen the physical universe behave in some odd ways. My life remains beautifully surreal in the meantime … Sam Bowen

We don’t and we never will. But Occam’s razor applies; is it simpler/more likely to assume that everything we perceive has been designed by a third-party intelligence, expending vast amounts of energy for unknown reasons, or that the world around us is real? My money is on the latter. SRF999

Does it matter? I don’t think it does. What does matter is how we respond to our perceived surroundings. Each of us has to adapt our responses in such a way that they affect our immediate environment so that we effect beneficial change. Such is intelligence. It doesn’t matter by whom or why the environment was constructed. The funny thing to note is that as a whole (as opposed to us acting as individuals), we appear to be failing big style. Bristol_Fashion

Hilary Putnam posed the question: how do we know that we are not just a brain in a vat. Putnam argued that to ask the question we needed to have a causal relationship with an external world and hence we could not possibly just be brains in a vat. My own view however is that this assumes that we can “peek” outside the box, which I do not think we can.

We could therefore very possibly be just brains in a vat (or just living in a simulation like the Matrix). It really depends on what you are asking. Most people assume that there has to be something else – either a god or external reality that contains our universe. So in effect yes we are just brains in a vat. But what is the vat?

I would suggest that language is the vat. Language is the DNA of the mind and we are living in a sea of language, which is creating the consciousness that we perceive. If you think about it, you can only pose the question that you did (“Are we in a simulation?”) because of language. It is language that enables that thought to be entertained and language that demands the answer. The physical, material world has no need for that question. It has all the answers it needs. It is only the human mind and the language that structures it that creates this need. soonah98

What does it matter? The objective of life is the same – try to enjoy yourself while making things better for others, your loved ones and society as a whole. Simon Ellis

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