Already in ancient times, philosophers imagined that there is no way of telling that the world around us is real or that other people have a mind of their own. Perhaps I am the only one who is real while the rest of the world is my imagination. This could all be a dream. Some major religions claim that gods created this universe and that we are like them. In the Bible, it is written that God said: “Let us make mankind in our image, in our likeness.”

For a long time, it was impossible to clarify why this world might not be real or how the gods might have created it. Recent advances in information technology have changed that. This universe could be a virtual reality. We are inclined to think that what our senses register is real, so we tend to ignore evidence to the contrary. For instance, you may think you see a pipe when watching an image of a pipe. The caption of the famous painting named The Treachery of Images of René Magritte makes you notice: this is not a pipe.

In 1977 science fiction writer Philip K. Dick was the first to claim that we do exist in a computer-generated reality. This is the simulation hypothesis. He came to this insight after experiencing psychosis. If he is right then his name suggests that our creators do like to joke around. Professor Nick Bostrom explored the probability of the simulation hypothesis being true in the simulation argument.

According to Bostrom, there could be many different human civilisations. The humans in those civilisations may at some point enhance themselves with biotechnology and information technology, live very long and acquire capabilities ordinary humans do not have. For that reason, these beings are not humans anymore and are called post-humans. A post-human might be a biological creature, a humanoid artificial intelligence or a combination of both. They might be brains-in-vats or have no physical body.

These post-humans might run simulations of their human ancestor civilisations, and we could be living in one of those simulations. Bostrom then argues that at least one of the following options must be true:

1. Nearly all real human civilisations end before entering the post-human stage.
2. In any post-human civilisation, only an extremely small number of individuals are interested in running simulations of human ancestor civilisations.
3. We almost certainly live inside a computer simulation.¹

The argument comes with the following assumptions that seem plausible but are not proven:

• The computing power of post-human civilisations suffices to run a large number of simulations of human ancestor civilisations.
• It is possible to simulate the human consciousness in a computer, perhaps in a limited form that appears realistic.¹

Bostrom concludes that if you think our civilisation will one day become post-human and run many simulations of human ancestor civilisations, you must believe we already live inside one.¹ It is a matter of probability. If we invent this technology in the next 10, 100 or 1,000 years, it will not happen later than that. By then, we will have done it. But millions of years have passed when it could have happened, so it probably did. If we do it within 100 years, and it could have happened a million years, the odds that it already happened might be (1,000,000 – 100) / 1,000,000 = 0.9999 or 99.99%.

Non-humanoid civilisations are probably not interested in running large quantities of simulations of humans. They might run a few for research, but it seems unlikely that our emotions and history entertain beings entirely different from us. And so, most simulations of human civilisations are likely to be run by post-humans.

The simulation argument comes with uncertainties. The computing power of the post-humans might not be sufficient. Or nearly all human civilisations die out before being able to build these simulations. Or perhaps post-humans will differ from us to the point that they will not be interested in running simulations of humans. And we may only know that once we have become post-humans and have acquired the ability to do this. Hence, Bostrom does not try to guess the likelihood of the options. He thinks we have no information as to whether this universe is real. But he may be wrong.

Latest update: 20 May 2023

Featured image: Inspired By The Treachery of Images.

1. Are You Living In a Computer Simulation? Nick Bostrom (2003). Philosophical Quarterly (2003) Vol. 53, No. 211, pp. 243-255.