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| NewScientist | 00 Month 2006 www.newscientist.co

SCIENCE has revealed much about theworld and our position within it.Generally, the ndings have beenhumbling. The Earth is not the centreo the universe. Our speciesdescended rom brutes. We are madeo the same stu as mud. We aremoved by neurophysiological signalsand subject to a variety o biological,psychological and sociologicalinfuences over which we have limitedcontrol and little understanding.

One o our remaining sources opride is technological progress. Likethe polyps that over time create coralree s, the many generations ohumans that have come be ore ushave built up a vast technological

in rastructure. Our habitat is nowlargely one o human making. The

act o technological progress is also ina sense humbling. It suggests that themost advanced technology we havetoday is extremely limited andprimitive compared with what ourdescendants will have.

I we extrapolate these expectedtechnological advances, and thinkthrough some o their logicalimplications, we arrive at anotherhumbling conclusion: the simulationargument, which has caused somestir since I published it three years ago.

The ormal version o the argumentrequires some probability theory, butthe underlying idea can be grasped

without mathematics. It starts withthe assumption that uture civilisa-tions will have enough computingpower and programming skills to beable to create what I call ancestorsimulations. These would be detailedsimulations o the simulatorspredecessors detailed enough orthe simulated minds to be consciousand have the same kinds oexperiences we have. Think o anancestor simulation as a very realisticvirtual reality environment, but onewhere the brains inhabiting the worldare themselves part o the simulation.

The simulation argument makes noassumption about how long it willtake to develop this capacity. Some

uturologists think it will happenwithin the next 50 years. But even i ittakes10 million years, it makes nodi erence to the argument.

Let me state what the conclusion o

the argument is. The conclusion is thatat least one o the ollowing threepropositions must be true:

1 Almost all civilisations at our levelo development become extinctbe ore becoming technologicallymature.2 The raction o technologicallymature civilisations that are interestedin creating ancestor simulations isalmost zero.3 You are almost certainly living in acomputer simulation.

How do we reach this conclusion?Suppose rst that the rst propositionis alse. Then a signi cant raction ocivilisations at our level o develop-ment eventually become technologi-cally mature. Suppose, too, that thesecond proposition is alse. Then asigni cant raction o these civilisa-

do we live in acomputer simulation?NICK BOSTROM

7/28/2019 Do We Live in a Computer Simulation

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tions run ancestor simulations.There ore, i both one and two are

alse, there will be simulated mindslike ours.

I we work out the numbers, we

nd that there would be vastly manymore simulated minds than non-simulated minds. We assume thattechnologically mature civilisationswould have access to enormousamounts o computing power.

So enormous, in act, that bydevoting even a tiny raction toancestor simulations, they would be

able to implement billions osimulations, each containing as manypeople as have ever existed. In otherwords, almost all minds like yourswould be simulated. There ore, by avery weak principle o indi erence,you would have to assume that youare probably one o these simulatedminds rather than one o the onesthat are not simulated.

Hence, i you think that propositionsone and two are both alse, youshould accept the third. It is notcoherent to reject all three.

It should be emphasised that thesimulation argument does not showthat you are living in a simulation. Theconclusion is simply that at least oneo the three propositions is true. It

does not tell us which one.In reality, we dont have much

speci c in ormation to tell us which othe three propositions might be true.In this situation, it might bereasonable to distribute our credenceroughly evenly between them.

Let us consider the options in a littlemore detail. Proposition one is

straight orward. For example, maybethere is some technology that everyadvanced civilisation eventuallydevelops and which then destroysthem. Let us hope this is not the case.Proposition two requires that there isa strong convergence among alladvanced civilisations, such thatalmost none o them are interested inrunning ancestor simulations. One canimagine various reasons that may leadcivilisations to make this choice. Yet

or proposition two to be true, virtuallyall civilisations would have to re rain.

I this were true, it would be aninteresting constraint on the utureevolution o intelligent li e.

The third possibility is philosophi-cally the most intriguing. I it is

correct, you are almost certainly livingin a computer simulation that wascreated by some advanced civilisation.What Copernicus and Darwin andlatter-day scientists have beendiscovering are the laws and workingso the simulated reality. These lawsmight or might not be identical tothose operating at the more

undamental level o reality where thecomputer that is running oursimulation exists (which, o course,may itsel be a simulation). In a way,our place in the world would be evenhumbler than we thought.

What kind o implications wouldthis have? How should it change theway you live your li e?

Your rst reaction might think thati three is true, then all bets are oand you would go crazy. To reasonthus would be an error. Even i we arein a simulation, the best methods o

predicting what will happen next arestill the amiliar ones extrapolationo past trends, scienti c modelling andcommon sense. To a rst approxima-tion, i you thought you were in a

simulation, you should get on withyour li e in much the same way as iyou were convinced that you wereleading a non-simulated li e at thebottom level o reality.

I we are in a simulation, could everknow or certain? I the simulatorsdont want us to nd out, we probablynever will. But i they choose to reveal

themselves, they could certainly doso. Another event that would let usconclude with a high degree ocon dence that we are in a simulationis i we ever reach a point when weare about to switch on our ownancestor simulations. That would bevery strong evidence against the rsttwo propositions, leaving us only withthe third.

Nick Bostrom is the director of theFuture of Humanity Institute at theUniversity of Oxford