The Simulation Argument

Here you can peruse the debate that followed the paper presenting the simulation argument. The original paper is here, as are popular synopses, scholarly papers commenting or expanding on or critiquing the first paper, and some replies by the author. The simulation argument continues to attract a great deal of attention. I apologize for not usually being able to respond to individual inquiries. I hope you might find what you're looking for on this page.

Are You Living In a Computer Simulation?


This paper argues that at least one of the following propositions is true: (1) the human species is very likely to go extinct before reaching a “posthuman” stage; (2) any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof); (3) we are almost certainly living in a computer simulation. It follows that the belief that there is a significant chance that we will one day become posthumans who run ancestor-simulations is false, unless we are currently living in a simulation. A number of other consequences of this result are also discussed.

"The Simulation Argument is perhaps the first interesting argument for the existence of a Creator in 2000 years." - David Pearce (exaggerated compliment)
"Thank you so much, Dr. Bostrom. You have proved that my psychiatrist was wrong all along." - Anonymous correpondent (misfiring compliment)

Is the Universe a Code?

Discussion on the simulation argument with Lex Fridman

On anthropics and the simulation argument with Sean Carroll

Explained by Elon Musk.

Is Reality Real? The Simulation Argument

Living in a Simulation: Philosophy Rap

The Simulation Argument: Why the Probability that You are Living in the Matrix is Quite High

Another popularization. (Has been translated into Spanish, Russian.)

Why Make a Matrix? And Why You Might Be In One

Yet another popularization, for Matrix-aficionados.

Are our heads in the cloud? Science fiction or fact?

There is a powerful logical argument that they [simulators who constructed the reality we experience] could very possibly be science fact.

How to Live in a Simulation


If you might be living in a simulation then all else equal you should care less about others, live more for today, make your world look more likely to become rich, expect to and try more to participate in pivotal events, be more entertaining and praiseworthy, and keep the famous people around you happier and more interested in you.

The Matrix as Metaphysics

On several Brains-in-vats and Matrix-like scenarios. Argues in support of what is also my contention, that the simulation-hypothesis is not a radical skeptical hypothesis.

Innocence Lost: Simulation Scenarios: Prospects and Consequences

Those who believe suitably programmed computers could enjoy conscious experience of the sort we enjoy must accept the possibility that their own experience is being generated as part of a computerized simulation. It would be a mistake to dismiss this as just one more radical sceptical possibility: for as Bostrom has recently noted, if advances in computer technology were to continue at close to present rates, there would be a strong probability that we are each living in a computer simulation. The first part of this paper is devoted to broadening the scope of the argument: even if computers cannot sustain consciousness (as many dualists and materialists believe), there may still be a strong likelihood that we are living simulated lives. The implications of this result are the focus of the second part of the paper. The topics discussed include: the Doomsday argument, scepticism, the different modes of virtual life, transcendental idealism, the Problem of Evil, and simulation ethics.

Are You a Sim?

Weatherson is prepared to accept the Simulation Argument up to, but not including, the final step, in which I use the Bland Principle of Indifference. In this paper, he examines four different ways to understand this principle and argues that none of them serves the purpose. (For my reply, see the paper below.) Note that Weatherson accepts the third disjunct in the conclusion of the Simulation Argument - i.e. that there are many more simulated human-like persons than non-simulated ones. By contrast, I do not accept this: I think we currently lack grounds for eliminating either of the three disjuncts.

Living in a Simulated Universe

We explain why, if we live in a simulated reality, we might expect to see occasional glitches and small drifts in the supposed constants and laws of Nature over time.

The Simulation Argument: Reply to Weatherson

My reply to Weatherson's paper (above). I argue he has misinterpreted the relevant indifference principle and that he has not provided any sound argument against the correct interpretation, nor has he addressed the arguments for this principle that I gave in the original paper. There are also a few words on the difference between the Simulation Argument and traditional brain-in-a-vat arguments, and on so-called epistemological externalism.

Simulation Scenarios

Covers many related issues, but may be hard to understand without the oral presentation that is meant to go with these 79 slides.

The Simulation Argument again

Short article by Brueckner in which he proffers "a new way of thinking about Bostrom's argument". (See below for my reply.)

The Simulation Argument: Some Explanations

My response to Brueckner (above), in which I argue that he has misconstrued the simulation argument. I also argue that he is mistaken in his critique of the idea that simulated beings may themselves create ancestor-simulations.

Historical Simulations - Motivational, Ethical and Legal Issues

A future society will very likely have the technological ability and the motivation to create large numbers of completely realistic historical simulations and be able to overcome any ethical and legal obstacles to doing so. It is thus highly probable that we are a form of artificial intelligence inhabiting one of these simulations. To avoid stacking (i.e. simulations within simulations), the termination of these simulations is likely to be the point in history when the technology to create them first became widely available, (estimated to be 2050). Long range planning beyond this date would therefore be futile.

Are we living in a Matrix? What Can Computers Tell Us About God?

An MIT computer science grad student theologizes.

Theological Implications of the Simulation Argument

Nick Bostrom’s Simulation Argument (SA) has many intriguing theological implications. We work out some of them here. We show how the SA can be used to develop novel versions of the Cosmological and Design Arguments. We then develop some of the affinities between Bostrom’s naturalistic theogony and more traditional theological topics. We look at the resurrection of the body and at theodicy. We conclude with some reflections on the relations between the SA and Neoplatonism (friendly) and between the SA and theism (less friendly).

I, Sim - An exploration of the Simulation Argument

A student's MA thesis

A Patch for the Simulation Argument

This article reports on a newly discovered bug in the original simulation argument. Two different ways of patching the argument are proposed, each of which preserves the original conclusion.

Natural Evil and the Simulation Hypothesis

Some theists maintain that they need not answer the threat posed to theistic belief by natural evil; they have reason enough to believe that God exists and it renders impotent any threat that natural evil poses to theism. Explicating how God and natural evil co-exist is not necessary since they already know both exist. I will argue that, even granting theists the knowledge they claim, this does not leave them in an agreeable position. It commits the theist to a very unpalatable position: our universe was not designed by God and is instead, most likely, a computer simulation.

Constraints on the Universe as a Numerical Simulation

A low-level physics simulation using the simplest simulation methods, which simulated our universe on a grid with finite resolution, would result in some potentially observable distortions of the simulated physics because of the rotational symmetry breaking effects of the simulation lattice. I would think that even the earliest simulations of systems sufficiently complex to contain observers would make use of powerful computational shortcuts that would eliminate the opportunity to observe any such discrepancies (mostly the simulation would take place at a much higher level of abstraction in order to reduce the computational demands).

On the 'Simulation Argument' and selective skepticism

Develops an objection similar to the one discussed under question 4 in the Q&A.

The Simulation Argument

A critical discussion in the context of the doomsday argument.

The Doomsday Argument and the Simulation Argument

Analyzes some analogies and disanalogies between the doomsday argument and the simulation argument, and concludes that the former fails while the latter succeeds.

Traditional philosophical skepticism and brain-in-a-vat arguments:

Skepticism: A Contemporary Reader

On anticipated technological capability of running realistic simulations:

Whole Brain Emulation: A Roadmap

Minimum energy requirements of information transfer and computing.

Superintelligence: Paths, Dangers, Strategies

Engines of Creation: The Coming Era of Nanotechnology.

How Long Before Superintelligence?

Nanosystems: Molecular Machinery, Manufacturing, and Computation.

Matrioshka Brains.

Nanomedicine: Volume 1: Basic Capabilities.

The Age of Spiritual Machines: When computers exceed human intelligence

Ultimate physical limits to computation

Mind Children

Robot: Mere Machine to Transcendent Mind

Pigs in Cyberspace

The Physics of Information Processing Superobjects: The Daily Life among the Jupiter Brains

The Physics of Immortality

Existential risks (How we could fail to develop the required technologies):

Existential Risks: Analyzing Human Extinction Scenarios and Related Hazards


Existential Risks Reduction as Global Priority

The methodology of observation selection effects:

Anthropic Bias: Observation Selection Effects in Science and Philosophy


The Planetarium Hypothesis: A Resolution of the Fermi Paradox

Some simulation-scenarios depicted in fiction:



Atlanta (S02E07): Bostrom’s Simulation Scene

Permutation City

The Matrix

The Thirteenth Floor

Vanilla Sky

Open Your Eyes (Abre los Ojos)

I don't know, Timmy, being God is a big responsibility

Welt am Draht

Note: This is by no means a complete list. Some others include Simulacron III (1963), aka Counterfeit World, by Daniel F. Galouye, which was made into the movie Welt Am Draht (1973) by Rainer Werner Fassbinder (The Thirteenth Floor was also based on Simulacron III); Exit to Reality (1997) by Edith Forbes; Otherland by Tad Williams (1996-2001); the film Dark City (1950, 1998); eXistenZ (film directed by David Cronenberg, 1999); many stories by Philip K. Dick; Realtime Interrupt (1995) by James P. Hogan, etc. etc. Jay Shreib produced a play inspired by the simulation argument, World of Wires, which opened in New York in January 2012.

Nick Bostrom

Photo of Nick Bostrom

Nick Bostrom’s homepage is at


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