The Simulation Hypothesis

Hey, today is #PhilosophyFriday ๐Ÿค”!

How about discussing some philosophical aspects of Computer Science? Today's question is:

โ“ How do you know you're not living in a simulation? ๐Ÿงต๐Ÿ‘‡

This idea is called the simulation hypothesis and it exists, in some form, way back in ancient Greek, Mayan, and Indian philosophy, passing through Descartes and Berkeley, and more recently popularized by Nick Bostrom.

The modern (and simplified) version goes like this ๐Ÿ‘‡


  • 1๏ธโƒฃ it is impossible to simulate a high-fidelity universe; or
  • 2๏ธโƒฃ any civilization capable of doing so has no interest in doing it; or
  • 3๏ธโƒฃ we are living in a simulated universe.

โ“ Stop now and tell me what do you think?

Let's analyze each alternative.

1๏ธโƒฃ It may well be that simulating a universe is impossible because of quantum mechanics or other unknown physical restrictions that we today don't understand. That is, high-fidelity physics might be uncomputable.

โ˜๏ธ But, there is little evidence for this, since we are already capable of simulating a nice chunk of physics, and it seems all we need is more computing power.

The advent of quantum computers might make this possible, even if very costly.

2๏ธโƒฃ If it's possible to simulate a high-fidelity universe, then any civilization that can do it in principle will do it, unless:

  • ๐Ÿ…ฐ๏ธ it is way too costly to be of any value; or
  • ๐Ÿ…ฑ๏ธ it is morally forbidden, out of a sense of respect for the simulated individuals' lives.

โ˜๏ธ Sadly we have little evidence that morals would stop the human civilization from simulating other individuals, giving our history. Maybe "mature" civilizations are different.

3๏ธโƒฃ If it's technically feasible and interesting for any civilization advanced enough to simulate a high-fidelity universe, then we are almost certainly living in one.

โ“ Why?

Either we are simulated or we are not.

In either case, with enough computing power, we will be able to simulate a universe ourselves, since this universe is either real or a high-fidelity simulation.

๐Ÿ’ก So there should be arbitrarily deep hierarchies of simulated universes.

Hence, what is more likely? That we just happen to be the one civilization at the top of the hierarchy, or that we are somewhere inside the hierarchy?

Without further prior evidence we must believe that all steps in the hierarchy are equally likely.

โ˜๏ธ So, we are simulated.

๐Ÿคฏ Think about the implications!

Either you believe simulating a universe is physically impossible or universally tabu, or you have to believe you are living inside a simulation!

โ“ Tell me again, what do you think now?

There are plenty of objections to this thought experiment but, in principle, if we were living inside a simulation, we could be unable to prove it, since any evidence we gather could be part of the simulation.

๐Ÿ˜ฌ So, science appears to have no way to attack this problem.

Recently, a compelling argument from @neiltyson has brought peace to my mind again, turning the hierarchy logic on its head.

โ˜๏ธ Given that almost all movies are based on the modern era, if we are simulated, why would we exist in the pre-simulation era?

๐Ÿ˜ In any case, if we are living inside a simulation, maybe it's better if we don't find out. That could be the "game over" after which the simulation is restarted.

As usual, if you like this topic, reply in this thread or @ me at any time. Feel free to โค๏ธ like and ๐Ÿ” retweet if you think someone else could benefit from knowing this stuff.

๐Ÿงต Read this thread online at

Stay curious ๐Ÿ––:

๐Ÿ—จ๏ธ You can see this tweetstorm as originally posted in this Twitter thread.