The key ideas

Reality+: Virtual Worlds and the Problems of Philosophy

David Chalmers, 2022

Can we prove that we are not living in a computer simulation? The philosopher David Chalmers thinks we can't, and then makes a surprising move: even if the world is simulated, that doesn't make it fake. The book takes you from the butterfly parable and Descartes' demon to a programmer god, and shows why a virtual life can be a real life.

Who it is for

For anyone who has ever caught themselves thinking “what if none of this is real?” And for everyone who spends a lot of time in games, social media and video calls and wants to know which part of it is real.

How do you know you're not in a computer simulation right now?

What the book is about

Imagine you are reading this page not in your own world, but inside a computer program. The sky outside the window, the cup in your hand and the noise of the street are all computed by a machine somewhere beyond your universe. The philosopher David Chalmers thinks this possibility can't be ruled out. But the real surprise is something else: even if it's true, your world doesn't become a fake.

Chalmers brings together the old questions of philosophy and new technology. He has a name for his approach: technophilosophy. The book's central claim sounds bold: virtual reality is genuine reality. Ahead of you are the parable of the butterfly, Descartes' demon, an argument for why we might be living in a simulation, and a creator of the world who could turn out to be a teenage hacker. And at the end, an answer to the question of whether you can live a good life in a virtual world.

Idea 1. Ancient sages asked the same questions as a virtual reality headset

One night the Chinese philosopher Zhuangzi dreamed he was a butterfly. When he woke up, he couldn't tell who he was: Zhuangzi who had dreamed of being a butterfly, or a butterfly now dreaming it was Zhuangzi.

Chalmers opens the book with three old stories. The butterfly dream raises a question about knowledge: can you know that you're not dreaming, or not in a virtual world? An Indian legend about a sage named Narada, whom the god Vishnu showed an entire other life, raises a question about reality: does what happens in an illusion really happen? Plato's cave, where prisoners spend their whole lives seeing only shadows on a wall, raises a question about value: can you live well if your whole world is made of shadows?

Chalmers's answers go like this. We can't know that we're not in a virtual world. Virtual worlds are real, not illusions. And a good life in them is possible.

What this means for you: arguments about virtual reality aren't child's play. They are the three great questions of philosophy, just dressed in new clothes.

In 2016, at a mobile technology conference, someone took a famous photo. In it, Mark Zuckerberg walks down the aisle while the whole hall sits in virtual reality headsets and doesn't notice him. Chalmers calls the photo a modern illustration of Plato's cave.

The question “is this real?” splits into three different ones: can you know it, does it exist, and is it a good way to live.

Read in Livria

About the author

David Chalmers is an Australian philosopher, a professor at New York University and one of the best known researchers of consciousness. He framed “the hard problem of consciousness”: why the workings of the brain come with experience at all.

All books by this author: David Chalmers

Terms from the book

  • Zuckerberg
  • Wheeler
  • Zhuangzi
  • Plato
  • Neuron
  • Quark
  • Photon
  • Terraforming
  • Consciousness
  • Virtual reality: A world created by a computer that a person is fully immersed in, for example through a headset. Chalmers takes “virtual” to mean “digital”, not “fake”.
  • Technophilosophy: Chalmers's term for an approach in which philosophy asks questions about technology, and technology helps answer the old questions of philosophy.
  • Narada: A sage from Indian legend. In the story Chalmers retells, he lives through an entire other life at the will of the god Vishnu.
  • Vishnu: One of the principal gods of Hinduism. In the legend of Narada he shows the sage the power of illusion.
  • Descartes: René Descartes, a 17th century French philosopher. In his Meditations on First Philosophy of 1641 he asked how we can know anything at all about the outside world.
  • Evil demon: Descartes' image of a powerful deceiver who could feed a person a picture of a world that does not exist.
  • Simulation: A world computed entirely by a computer. In the book the word usually refers to large worlds that we ourselves might be living in.
  • Simulation hypothesis: The idea that we have spent our whole lives inside a computer simulation.
  • Matrix: The Matrix, a 1999 film in which the ordinary world turns out to be a computer program wired into people's brains. Chalmers refers to it often.
  • Quaid: Douglas Quaid, the hero of the film Total Recall. Right to the end, the viewer doesn't know whether his adventures on Mars were real or virtual.
  • Bostrom: Nick Bostrom, a Swedish-born philosopher. In 2003 he put forward the simulation argument.
  • Simulation argument: The reasoning that if civilizations learn to create many worlds with conscious beings, simulated beings will outnumber ordinary ones, and we are probably among them.
  • Sim blocker: Chalmers's term for anything that could prevent large numbers of simulated beings from coming into existence. For example, civilizations dying out, or consciousness being impossible in a computer.
  • Nadine: A character in the series Atlanta who decides that if the world is a simulation, then everyone is fake. Chalmers cites her words as an example of a mistake.
  • Bit: The smallest unit of information in a computer: a zero or a one.
  • It from bit: Wheeler's idea that at the very bottom of the physical world there may be information, that is, computation with bits.
  • Nozick: Robert Nozick, a 20th century American philosopher. He devised the thought experiment of the experience machine.
  • Experience machine: A device from Nozick's thought experiment that gives a person any experiences they like while they float in a tank with electrodes attached.
  • Second Life: A virtual world launched in 2003, where people live for years through their characters: building houses, working, making friends.
  • Moral status: The property of a being that makes its interests matter, so that it cannot be treated any way you please.

All terms

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