Are we living in a simulation?
Which of Bostrom's three possibilities is true?
I
We are probably simulated
The third disjunct is the likeliest. Given what we know, we should assign a significant probability to being in a simulation.
- Best argument
- There is no known physical law forbidding the computing power required, and our own civilisation is visibly heading toward ever more detailed simulations. If even a small fraction of civilisations run many simulations, simulated minds would dominate. If you have no evidence about whether you are simulated, the principle of indifference says you should assume you are typical, and the typical mind would be simulated.
- Strongest objection
- Each step involves enormous uncertainty: whether consciousness can be simulated, whether posthumans would want to, whether the computing power is possible. Multiplying uncertainties does not produce a confident conclusion.
- The reply
- Bostrom agrees, which is why he presents the argument as a three-way disjunction rather than a proof.
- Defended by
- Elon Musk
II
The trilemma holds, but not option three
The argument is valid, but options one or two are more likely: civilisations die out, or do not run such simulations.
- Best argument
- There are many reasons civilisations might not run ancestor simulations: ethical concerns about creating billions of suffering people, lack of interest, or regulations. And perhaps no civilisation survives long enough. The argument does not tell us which option is true; it is a reason to worry about option one as much as to wonder about option three.
- Strongest objection
- Options one and two require near-universal agreement across all civilisations. If even a small number of eccentric individuals with enough power run simulations, the numbers swing toward option three.
- Defended by
- Nick Bostrom
III
The argument does not work
The argument rests on false or untestable assumptions, especially that simulated beings would be conscious and that we can reason about our 'typicality' this way.
- Best argument
- If consciousness depends on biology, simulated people would not be conscious, so there would be no simulated observers to outnumber us. The indifference principle is also questionable: we know we are conscious and embodied, and the reference class of 'all observers' may be ill defined. And a hypothesis that predicts nothing different from the real-world hypothesis may not be a hypothesis at all.
- Strongest objection
- Doubts about machine consciousness are themselves uncertain, and even a modest probability that simulated beings are conscious keeps the argument alive.
- Defended by
- John Searle, Sabine Hossenfelder
IV
It would not matter much
Even if we are simulated, our world is real: the objects around us exist as computational structures, and our lives are no less meaningful.
- Best argument
- David Chalmers argues that the simulation hypothesis is not a skeptical hypothesis but a metaphysical one. If we are in a simulation, then tables, trees and people exist; they are just made of bits rather than (or as well as) particles. Virtual objects, on his view, are real objects.
- Strongest objection
- Many people feel that discovering their world was a simulation would be devastating, not neutral. It would mean that its creators could end it, edit it, or watch it.
- Defended by
- David Chalmers
For the full background, variations and open questions, read the entry: Are we living in a simulation?.