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A Physicist Rejects the Idea That We Live in a Sim Universe

At IAI News, Marcelo Gleiser worries that the claim that we are simulated beings with no free will reduces our ability to tackle the problems humanity faces

Dartmouth College physicist Marcelo Gleiser insists that the reality in which we live is not a simulation by advanced aliens or other intelligences — and that the fact that it isn’t is important. As the summary of his essay at IAI News explains,

The idea that we are living in a simulation has become commonplace. Elon Musk, for example, thinks it is almost certain we are living in a simulation. But the simulation hypothesis comes up against insurmountable problems, and is, in the end, an excuse for us not to sort out our real moral failings…

Marcelo Gleiser, “Reality is not a simulation and why it matters” at IAI News (January 4, 2023)

The “simulation” idea may sound pretty far-fetched but it is more popular than some might expect. Science broadcaster Neil deGrasse Tyson, driverless car entrepreneur Elon Musk, and former Astronomer Royal Martin Rees have aired the idea. Philosopher of consciousness David Chalmers argues that we can’t prove we are not living in a simulation.

First, Gleiser agrees with Chalmers that, from a philosophical perspective, a sim universe is not self-evidently false. A claim that the average cat has six legs, for example, can easily be falsified — and we don’t need philosophy to do it. But how do we show that Tyson, Musk, and Rees are mistaken?

Gleiser traces the history of the modern sim universe to a paper by Oxford philosopher Nick Bostrom, “Are We Living in a Simulation?” (2003) Gleiser summarizes the argument: “Bostrom’s point is that if our species survives the transition to a new, posthuman phase, the ‘new us’ will have unimaginable computational powers, and running realistic simulations will be a given. If this is the case, we in the present would be like characters in a super-advanced Sims game, convinced that we have autonomy when, in fact, we are puppets in the hands of the game-players.”


Among those who search for intelligent life beyond Earth, there is also the Planetarium Hypothesis, where advanced extraterrestrials, rather than our own descendants, are supposed to be our simulators. At Universe Today, Matt Williams notes, “to break it down, this hypothesis states that the reason we are not seeing aliens is that humanity is in a simulation, and the aliens are the ones running it! In order to ensure that human beings do not become aware of this fact, they ensure that the simulation presents us with a “Great Silence” whenever we look out and listen to the depths of space.” (August 27, 2020)

Some hope for experiments that will provide evidence of simulation:

More realistically, physicists have proposed experiments that could yield evidence that our world is simulated. For example, some have wondered if the world is inherently “smooth,” or if, at the smallest scales, it might be made up of discrete “chunks” a bit like the pixels in a digital image. If we determine that the world is “pixelated” in this way, it could be evidence that it was created artificially. A team of American and German physicists have argued that careful measurements of cosmic rays could provide an answer.

Dan Falk, “Are we living in a simulated universe? Here’s what scientists say.” at NBC News (July 6, 2019)

Physicist Melvin Vopson suggests looking for glitches in the sim:

The late physicist John Barrow has argued that a simulation would build up minor computational errors which the programmer would need to fix in order to keep it going. He suggested we might experience such fixing as contradictory experimental results appearing suddenly, such as the constants of nature changing. So monitoring the values of these constants is another option.

Melvin Vopson, “How to test if we’re living in a computer simulation” at The Conversation (November 21, 2022)

Yes, it all sounds pretty far-fetched. Still, disbelief isn’t, by itself, an argument against it. Gleiser offers a more philosophical reason for doubt: How do we know that our simulators are not themselves simulated by earlier ones, in an infinite regress backwards in time? In theology, God — who is beyond nature — is posited as the First Cause by definition, which prevents that problem. But the non-theistic sim cosmos proposed does not have that option. And, incidentally, in the absence of a First Simulator, the theorists will encounter major logical problems with a universe that is infinite in past time anyway.

Gleiser fears that taking a sim universe seriously means abandoning the concept of free will just when we need it:

The simulation argument messes with our self-esteem, assuming that we have no free will, that we are just deluded puppets thinking we are autonomous beings, free to make choices. To believe this is to give up our sense of autonomy: after all, if it’s all a big game that we can’t control, why bother? What difference could my actions or sense of purpose make? “Let the world go to hell, as it is now. We can’t change it anyway.”

Marcelo Gleiser, “Reality is not a simulation and why it matters” at IAI News (January 4, 2023)

But the awkward problem is that we either do or don’t have free will. The strenuously debated question doesn’t depend on whether we live in a sim universe. After all, we could be automatons in an accidental universe where free will is an illusory concept. Alternatively, we could be living in a universe created by an all-powerful supernatural being that did not give us free will. In none of these cases though is it clear how we would even know about it free will.

Free will seems more like one of those things that we wouldn’t know about if we didn’t have it. That may be one of the stronger arguments against the sim hypothesis.

You may also wish to read: How can we believe in naturalism if we have no choice?

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A Physicist Rejects the Idea That We Live in a Sim Universe