Reality+ by David J Chalmers review – are we living in a simulation?

A mind-bending philosophical investigation that argues virtual worlds are just as real as anything else we experience

In the Wachowskis’ 1999 film The Matrix, the humdrum life of the central character Neo is revealed to be an illusion. His green-tinted reality is actually a digital simulation created by connecting human brains to a computer. When Neo swallows the red pill offered to him by Morpheus, his body is disconnected from the computer system and he is plunged into a new and frightening reality: for the first time he experiences the physical world.

But as philosopher David Chalmers points out, how does Neo know that this new reality is not just another convincing simulation? Or, as the Professor Cornel West (who played Councillor West of Zion in The Matrix Reloaded) puts it: “It’s illusions all the way down.” This is the mind-boggling philosophical rabbit hole into which Chalmers invites his reader to dive headlong: is this – to paraphrase Bohemian Rhapsody – the real world, or is it just fantasy?

Although Chalmers’s interest in virtual reality as a philosophical problem began when he was asked to write an essay for the official website of The Matrix at the time of its release, he now disagrees with the film’s premise – namely, that the digital simulation from which the film takes its name is an illusion. “Neo’s world is perfectly real,” he writes. Over 544 pages, Chalmers argues that virtual reality (VR) is in fact “genuine reality”.

Chalmers taught himself to write computer programs at the age of 10 and discovered his first virtual world in 1976, the text-based Colossal Cave Adventure. Today he regularly uses different VR systems: “I put on a headset, open an application, and suddenly I’m in a virtual world,” he writes. In VR he has assumed a female body, visited Mars, grappled with assassins, and taken to the skies like a bird. During the pandemic he regularly used it to discuss philosophy, meeting up with his “merry band of fellow philosophers”. Although the technology may still be somewhat clunky, he notes, “we had the sense of inhabiting a common world”.

Facebook’s recent rebranding as Meta – short for “metaverse”, a term borrowed from Neal Stephenson’s 1992 novel Snow Crash – signalled the growing importance of these new immersive cyber technologies. Facebook’s Oculus Quest headset is already available and Apple is due to release one soon. Augmented reality (AR) is also improving, offering a way of experiencing the world that is part virtual and part physical, with digital objects or text overlaid across the visual field. Chalmers thinks AR could initially be more influential than VR, replacing screen-based computing entirely.

As the technology progresses, AR glasses or contact lenses may be superseded by retinal or brain implants. A brain-computer interface would allow our eyes and other sense organs to be bypassed, affording access to a complete range of simulated sensual experiences. Ultimately, this will transform how we live, work and think: “My guess is that within a century we will have virtual realities that are indistinguishable from the nonvirtual world,” Chalmers predicts.

He believes that eventually many people will spend most of their lives in these environments, just as today people choose to emigrate to another country: “Given all the ways in which virtual worlds may surpass the nonvirtual world,” he writes, “life in virtual worlds will often be the right life to choose.”

Chalmers rejects the idea that digital experiences are always mere escapist fantasies, as they might be in video games: “Simulations are not illusions. Virtual worlds are real. Virtual objects are real.” They are clearly not the same as non-virtual objects, but a virtual chair is created using digital processes, just as a physical chair is made of atoms and quarks.

It follows that what happens in virtual worlds really does happen. You could lead your entire life in one and find it meaningful and fulfilling. Indeed, Chalmers argues that we could already be inhabitants of a virtual reality: “We can never prove we’re not in a computer simulation because any evidence of ordinary reality could be simulated.”

This is known as the simulation hypothesis, the scenario that is explored in the recently released Matrix Resurrections. Chalmers points out that humans have already invented games that simulate real life, such as The Sims. These will become more sophisticated over time, with versions of them running on millions of devices. Furthermore, out there in the rest of the universe, “if any aliens have human-level intelligence, they should eventually develop computers and program them. If these alien civilisations survive long enough, they’ll likely create simulated universes.” Statistically speaking, that means simulated beings probably already vastly outnumber “real” ones. In other words, it’s more likely we’re living in a simulation than in the original version of our world.

If we are indeed living in a simulation, then the creator of it is our god, be that a mad scientist, an alien or a teenage girl who has pressed a button in SimUniverse and set us going. As an atheist, says Chalmers, “the simulation hypothesis has made me take the existence of a god more seriously than I ever had before”.

Ultimately, Reality+ is about extending our sense of the real. Chalmers’s central idea, that “there is more to reality than we thought”, is seductive, and I was surprised to find his arguments delightfully – or perhaps worryingly – convincing.

He has taken a subject most people would dismiss as pure science fiction and produced a brilliant and very readable philosophical investigation. The whole thing is an exercise in what Chalmers calls “technophilosophy” – asking philosophical questions about technology and using new technology to answer philosophical problems. He tackles some frankly mindbending ideas, but does so in a lively and entertaining style, filled with references to pop culture. The only question is whether you really want to know how deep the rabbit hole goes. But then, what do you have to lose but your illusions?

• Reality+: Virtual Worlds and the Problems of Philosophy is published by Allen Lane (£25). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply.