The big idea: are we living in a simulation?

Elon Musk thinks you don’t exist. But it’s nothing personal: he thinks he doesn’t exist either. At least, not in the normal sense of existing. Instead we are just immaterial software constructs running on a gigantic alien computer simulation. Musk has stated that the odds are billions to one that we are actually living in “base reality”, ie the physical universe. At the end of last year, he responded to a tweet about the anniversary of the crude tennis video game Pong (1972) by writing: “49 years later, games are photo-realistic 3D worlds. What does that trend continuing imply about our reality?” This idea is surprisingly popular among philosophers and even some scientists. Its modern version is based on a seminal 2003 paper, Are We Living in a Computer Simulation? by the Swedish philosopher Nick Bostrom. Assume, he says, that in the far future, civilisations hugely more technically advanced than ours will be interested in running “ancestor simulations” of the sentient beings in their distant galactic past. If so, there will one day be many more simulated minds than real minds. Therefore you should be very surprised if you are actually one of the few real minds in existence rather than one of the trillions of simulated minds.

This idea has a long history in philosophical scepticism (the idea that we can’t know anything for sure about the external world) and other traditions. The Chinese Taoist sage Zhuangzi wrote a celebrated fable about a man who couldn’t be sure whether he was a man dreaming of being a butterfly, or a butterfly dreaming of being a man. René Descartes imagined that he might be being manipulated by an “evil demon” (or “evil genius”) that controlled all the sensations he experienced, while the 20th-century American philosopher Hilary Putnam coined the term “brain in a vat” to describe a similar idea. But while Neo in the Wachowskis’ 1999 film The Matrix really is a brain (or rather a whole depilated body) in a vat, the simulation hypothesis says that you do not have a physical body anywhere. “You” are merely the result of mathematical calculations in some vast computer.

There are many possible objections to this idea even getting off the ground, as Bostrom notes. Perhaps it is simply not possible for computer-simulated beings to become conscious in the way we are. (This would defeat the “assumption of substrate independence”, according to which minds are not dependent on biological matter.) Or perhaps all civilisations destroy themselves before getting to the simulation stage. (Plausible if not necessarily comforting.) Or perhaps advanced civilisations are simply not interested in running such simulations, which would be surprising given the kinds of things humans do – such as developing video deep-fake technology or researching how to make viruses more virulent – even though they seem to be very bad ideas. The simulation hypothesis is perhaps attractive to a wider culture because of its nature as a cosmic-scale conspiracy theory as well as an apparently scientific version of Creationism. The inconceivably advanced alien running its simulation of our universe is indistinguishable from traditional terrestrial ideas of God: an all-powerful being who designed everything we see.