Reading · further reading
The site doesn’t try to teach the literature. It points you to it. The difficulty tags are rough. easy is one sitting. medium takes real study. hard assumes a technical background, or the Library open beside it.
Nick Bostrom · Philosophical Quarterly, 2003
The original paper, and where the trilemma comes from.
Reality+: Virtual Worlds and the Problems of Philosophymedium
David Chalmers · W. W. Norton, 2022
The fullest book on the subject. It argues that simulated worlds can be truly real (simulation realism).
Beane, Davoudi & Savage · arXiv, 2012
Asks what we could observe if spacetime were simulated on a lattice, such as a directional bias in cosmic-ray spectra.
Seth Lloyd · Nature, 2000
Where the 5 × 10^50 operations per second per kilogram limit comes from. It’s the ceiling on every ladder on the site.
Whole Brain Emulation: A Roadmapmedium
Anders Sandberg & Nick Bostrom · Future of Humanity Institute technical report, 2008
Where the mind-model figures come from, level by level.
Simulating Physics with Computershard
Richard Feynman · International Journal of Theoretical Physics, 1982
The argument that ordinary computers can’t efficiently simulate typical quantum systems.
Irreversibility and Heat Generation in the Computing Processhard
Rolf Landauer · IBM Journal, 1961
The least energy it takes to erase a bit. The Power tile is built on it.
Rechnender Raum (Calculating Space)hard
Konrad Zuse · Vieweg, 1969; English translation MIT, 1970
The first proposal that physics is the output of a cellular automaton. It was digital physics before the name existed.
Digital Mechanicshard
Edward Fredkin · Physica D 45, 1990
Physics as a reversible universal cellular automaton, where information is the thing that’s conserved.
A New Kind of Sciencemedium
Stephen Wolfram · Wolfram Media, 2002
Simple programs that produce complex behaviour, and the claim that the laws of physics may be one of them.
Programming the Universeeasy
Seth Lloyd · Knopf, 2006
The universe as a quantum computer, by the author of the limit behind the site’s ceilings.
Max Tegmark · Foundations of Physics 38, 2008
A stronger claim: physical reality is a mathematical structure, whether or not it’s computed.
Franco Vazza · Frontiers in Physics 13, 2025
The energy it would take to simulate this universe, or Earth at different resolutions, compared with what a universe like ours holds. Summarised on the Tests page.
David H. Wolpert · Journal of Physics: Complexity 6, 2025
A formal treatment. Under the physical Church–Turing thesis a universe can simulate itself, and some questions about simulations can’t be decided.
Zohar Ringel & Dmitry Kovrizhin · Science Advances 3, 2017
Some quantum systems resist one kind of classical simulation. It’s often wrongly reported as disproving the hypothesis. It doesn’t.
What Is It Like to Be a Bat?medium
Thomas Nagel · Philosophical Review, 1974
The classic argument that experience is subjective in a way that can’t be reduced to anything else.
Epiphenomenal Qualiamedium
Frank Jackson · Philosophical Quarterly, 1982
The knowledge argument: Mary the colour scientist, and the claim that knowing every physical fact still isn’t knowing everything.
The Conscious Mindhard
David Chalmers · Oxford, 1996
Lays out the hard problem and defends property dualism.
Consciousness Explainedmedium
Daniel Dennett · Little, Brown, 1991
The main opposing view: that the hard problem breaks up into a set of solvable problems about function.
Meditations on First Philosophymedium
René Descartes · 1641
The evil demon, an early scenario of radical doubt, and the cogito as the thing that survives it.
Brains in a Vathard
Hilary Putnam · in Reason, Truth and History, 1981
Argues, from semantic externalism, that the vat hypothesis can’t be coherently stated from inside it.
Anarchy, State, and Utopiamedium
Robert Nozick · Basic Books, 1974
Chapter 3 has the experience machine argument.
plato.stanford.edu
Peer-reviewed and free. Good entries to look up include consciousness and skepticism.
iep.utm.edu
A free, gentler counterpart to the Stanford Encyclopedia.
arXivhard
arxiv.org
Free preprints in physics. The Lloyd and Beane et al. papers above are hosted here.
To see what each experiment and physical bound found, go to Tests.
14 short pages, one per thinker, each with its matching sandbox dial.