Anthony Campbell

How to Tell if You Live in a Simulation

Last revised 11 April 2021

"[The Red King is] dreaming now," said Tweedledee: "and what do you think he's dreaming about?"
Alice said: "Nobody can guess that."
"Why, about you! Tweedledee exclaimed, clapping his hands triumphantly. "And if he left off dreaming about you, where do you suppose you'd be?"
"Where I am now, of course," said Alice.
"Not you!" Tweedledee retorted contemptuously. "You'd be nowhere. Why, you're only a sort of thing in his dream!"
"If that there King was to wake," added Tweedledum, "you'd go out—bang!—just like a candle!"
"I shouldn't!" Alice exclaimed indignantly. "Besides, if I'm only a sort of thing in his dream, what are you, I should like to know?"
"Ditto", said Tweedledum.
"Ditto ditto," cried Tweedledee.
He shouted this so loud that Alice couldn't help saying, "Hush! you'll be waking him, I'm afraid, if you make so much noise."
"Well, it's no use your talking about waking him," said Tweedledee, "when you're only one of the things in his dream. You know very well you're not real."
"I am real!" said Alice, and began to cry.
"You won't make yourself a bit realler by crying," Tweedledee remarked: "there's nothing to cry about."
"If I wasn't real," Alice said—half-laughing through her tears, it all seemed so ridiculous—"I shouldn't be able to cry."
"I hope you don't suppose those are real tears?" Tweedledum interrupted in a tone of great contempt.

[Lewis Carroll: Through the Looking-Glass]

An ancient dilemma given a modern twist

Alice's dilemma is a very ancient one. The seventeenth-century Spanish playwright Calderón used it in his play Life is a Dream, and long before him the Chinese Taoist sage Chuang Tzu said on waking that he could not be sure if he was a man who had dreamt he was a butterfly or a butterfly who had dreamt he was a man. Such ideas find their modern technological counterpart in the Simulation Hypothesis, which proposes that the whole of reality—/the entire universe—is an artificial simulation.

Taking the simulation hypothesis seriously

The simulation hypothesis is not just science fiction; some recently published papers by mainstream philosophers and scientists, including Nick Bostrom,1 David Chalmers,2 and Martin Rees3 among others, have taken it seriously, and it was recently discussed in the BBC popular science programme 'The Infinite Monkey Cage'.

Who is thought to be responsible for this computer simulation? The usual answer is: our own remote descendants, who are supposed to have taken computing power far beyond what exists today. It's equally conceivable that the simulators could be non-human beings on other planets, in other galaxies, or even in other universes.

The religious angle

It's surprising (or perhaps not) that, as far as I know, the simulation hypothesis hasn't been taken up by theologians. It should be. It may afford evidence of the existence of God, or gods, at least in a technological sense. And of course it would readily accommodate the notions of heaven and hell.

The simulators would have the status of gods so far as we are concerned. They have created us, they could destroy us, and they can interfere in our world whenever they choose. Bostrom tells us that a correspondent who had been a life-long hard-core atheist has now become an agnostic after reading about the simulation hypothesis!

But agnostic about what, exactly? Presumably not the Christian God, omnipotent and omniscient. The simulator(s) of our world would have to be super-intelligent but not necessarily unlimited in power and knowledge. In fact, he (she, it, they according to taste) would be like the Demiurge that Plato and his successors, including the Gnostics, envisaged.

The Demiurge doesn't create the world out of nothing but takes the existing matter and rearranges it. I should say the world as we have it corresponds better to this idea than to the conventional Christian view; it contains plenty of imperfections. The Demiurge did his best but some things were beyond his power—hence the existence of evil.

The ethical question

Christopher Langton, described by John Horgan as the founding father of artificial life, holds that simulations of life run on a computer are literally alive. He said to Horgan: "I like to think that if I saw somebody sitting next to me at a computer terminal who is torturing these creatures, you know, sending them to some digital equivalent of hell, or rewarding only a select few who spelled out his name on the screen, I would try to get this guy some psychological help!".4.

Might not ethical issues exist for our simulators too? Wouldn't they feel responsible for our wellbeing? They might feel that, in creating us, they had created an autonomous life form to which they had obligations. This might make it difficult for them just to switch us off.

And here's another thought. Would the simulators be happy to leave us in perpetual ignorance of the real state of affairs, and of their existence, or would they wish to make themselves known to us, as God is supposed to have done in revelation?

I think they might. But how would they go about it?

They could, presumably, alter the code so that we were simply naturally aware of the situation in which we found ourselves. We would then be living in a different kind of world, in which we all just knew, without question, that we were simulations. But the simulators might be reluctant to do so because it would alter the nature of the simulation too radically and perhaps destroy its purpose, whatever that is.

Planting clues in the simulation

So what's the alternative? Well, they could plant clues in the simulation to give us subtle hints, nudges in the right direction. They could create occasional anomalies in our world which were intended to act as clues.

These anomalies should not be too glaring or everything would break down and science would become impossible. At the same time, they should be sufficiently incompatible with the results of our scientific inquiry that they could not be explained within a rationalist world view, otherwise they would not have the power to disturb us. They would be borderline phenomena, exceptions to the laws of nature as we experience them but occurring only rarely and unpredictably. It would be difficult or impossible to be sure that they really were exceptions; it should always be more or less possible for us to explain them away. This would require fine judgement on the part of the simulators but it should be manageable.

But isn't this is what we actually find in our world?

Anomalous events in our world

In general, the universe follows what we describe as laws of nature. It makes sense. (Incidentally, the simulation hypothesis explains the otherwise mysterious fact that the universe is lawful rather than chaotic—something that troubles philosophically-minded scientists. It also explains the fine tuning problem.)

And yet this lawfulness does have apparent exceptions. As far back as written records go there have been reports of what we now term the paranormal. Hauntings, premonitions, apparitions, and similar phenomena have been described throughout history. And there is a wealth of anomalous events, some involving thousands of witnesses, in the religious literature; see, for example, the Wikipedia article Marian apparition. And then there is the huge volume of UFO literature.

In the nineteenth century a group of British intellectuals came together and founded the Society for Psychical Research (SPR) to study such phenomena; the American Society for Psychical Research soon followed (the philosopher and psychologist William James was a prominent member).

Sceptics generally dismiss all this out-of-hand, as due to superstition, fraud, or misreporting. But sometimes maintaining this attitude is difficult, at least if one takes an objective view of the reported facts. Not all scientists are dismissive of the paranormal; for example, Bernard Carr, professor of mathematics and astronomy at Queen Mary University of London, is a past President of the SPR.5

A good example of a hard-to-explain anomaly of this kind is the literature on poltergeists. The difficulty of accounting for such reports in a rationalist manner has been well brought out by Alan Gauld and A.D. Cornell.7 I concluded my review of their scholarly book by saying that "the authors have a lot of first-hand experience of the matter and I have none. I therefore have to keep an open mind about it, but, if they are right, the world must be a much stranger place than we rationalists like to think it is."

The simulation hypothesis provides a comprehensive explanation for such anomalies. They were put there by the simulators on purpose to keep us guessing.

The cosmic intelligence test

The existence of anomalies of this kind could be construed as a kind of cosmic intelligence test, designed to make us suspect that reality is different from how it appears to us. That idea is an ancient one. We find it, for example, in the mediaeval Islamic sect known as the Ismailis (see my book The Assassins of Alamut). The Ismailis believed that the Koran contained an inner significance, an esoteric secret to which they alone held the key, and they went on to construct a theosophy of extraordinary richness and complexity. Similar ideas are to be found in the Kabbalah, among the Cathars of the Languedoc in the Middle Ages, and in the gnostic texts. An underlying theme in such belief systems is the notion that the world as we experience it is unreal, a mere seeming, masking some unknown ultimate reality. The Indian concept of Maya expresses a similar idea and it's central to the philosophy of Kant. For a fictional treatment see David Lindsay, A Voyage to Arcturus

Esoteric systems like those I've mentioned usually include a hierarchical cosmology, with successive layers of reality culminating at the Absolute or Divine level. A similar suggestion has been made in the case of the simulation hypothesis: perhaps the beings who are simulating us are themselves being simulated, and so on.


Can we take all this seriously? As a sceptical materialist, I prefer to think that the anomalous features in our world can in the end be explained rationally—this is my default position. And I find that the simulation hypothesis, though a fun idea to play with, probably isn't true. Yet it is being taken seriously today by thoughtful people, and if you are one of them I think you should also take seriously the notion that the anomalous features in our world have been placed there deliberately by the simulators. Conversely, if you believe in the reality of paranormal phenomena or religious visions, probably you should also take the simulation hypothesis seriously.


  1. Nick Bostrom: Are you living in a computer simulation?
  2. Chalmers D: The Matrix as Metaphysic.
  3. Martin Rees: In the Matrix.
  4. John Horgan: The End of Science [p.200].
  5. Gauld A, (1968): The Founders of the Society for Psychical Research. Routledge and Kegan Paul, London.
  6. Wikipedia: Bernard Carr.
  7. Gauld A, Cornell AD (1979): Poltergeists, Heinemann, London.