The Matrix got many otherwise not-so-philosophical minds ruminating on the nature of reality. But the scenario depicted in the movie is ridiculous: human brains being kept in tanks by intelligent machines just to produce power.

There is, however, a related scenario that is more plausible and a serious line of reasoning that leads from the possibility of this scenario to a striking conclusion about the world we live in. I call this the simulation argument. Perhaps its most startling lesson is that there is a significant probability that you are living in computer simulation. I mean this literally: if the simulation hypothesis is true, you exist in a virtual reality simulated in a computer built by some advanced civilisation. Your brain, too, is merely a part of that simulation. What grounds could we have for taking this hypothesis seriously? Before getting to the gist of the simulation argument, let us consider some of its preliminaries. One of these is the assumption of “substrate independence”. This is the idea that conscious minds could in principle be implemented not only on carbon-based biological neurons (such as those inside your head) but also on some other computational substrate such as silicon-based processors.

Of course, the computers we have today are not powerful enough to run the computational processes that take place in your brain. Even if they were, we wouldn’t know how to program them to do it. But ultimately, what allows you to have conscious experiences is not the fact that your brain is made of squishy, biological matter but rather that it implements a certain computational architecture. This assumption is quite widely (although not universally) accepted among cognitive scientists and philosophers of mind. For the purposes of this article, we shall take it for granted.

Given substrate independence, it is in principle possible to implement a human mind on a sufficiently fast computer. Doing so would require very powerful hardware that we do not yet have. It would also require advanced programming abilities, or sophisticated ways of making a very detailed scan of a human brain that could then be uploaded to the computer. Although we will not be able to do this in the near future, the difficulty appears to be merely technical. There is no known physical law or material constraint that would prevent a sufficiently technologically advanced civilisation from implementing human minds in computers.

Our second preliminary is that we can estimate, at least roughly, how much computing power it would take to implement a human mind along with a virtual reality that would seem completely realistic for it to interact with. Furthermore, we can establish lower bounds on how powerful the computers of an advanced civilisation could be. Technological futurists have already produced designs for physically possible computers that could be built using advanced molecular manufacturing technology. The upshot of such an analysis is that a technologically mature civilisation that has developed at least those technologies that we already know are physically possible, would be able to build computers powerful enough to run an astronomical number of human-like minds, even if only a tiny fraction of their resources was used for that purpose.

If you are such a simulated mind, there might be no direct observational way for you to tell; the virtual reality that you would be living in would look and feel perfectly real. But all that this shows, so far, is that you could never be completely sure that you are not living in a simulation. This result is only moderately interesting. You could still regard the simulation hypothesis as too improbable to be taken seriously.

Now we get to the core of the simulation argument. This does not purport to demonstrate that you are in a simulation. Instead, it shows that we should accept as true at least one of the following three propositions:

1. The chances that a species at our current level of development can avoid going extinct before becoming technologically mature is negligibly small

2. Almost no technologically mature civilisations are interested in running computer simulations of minds like ours

3. You are almost certainly in a simulation.

Each of these three propositions may be prima facie implausible; yet, if the simulation argument is correct, at least one is true (it does not tell us which).

Discuss.

Another interesting thought:

Perhaps our reality is the training ground for future minds of a lower level reality. Much like the learning to learn model of public schooling, perhaps things like Christian law etc. are the rules that guide the mind until "birth" into the "real" world, and pergatory is where you are picked to move on and uploaded into a physical body.

That is what I would call a model society.

I believe the earth will be no more before any such advancements could or will be made.

From a scientific p.o.v natural selection is a constant war which medicine will never win. The diversity of views accross the planet will in time cause us to self destruct. Realistically someone could pull the plug on earth at any given time with biological weaponry, created supposedly to protect us.

Any country making a discovery like this would basically instigate a global war anyway.

What about the arguement we are already in it.

For all we know, we could be a very elaborate gave of Sid Meier's Civilization on a computer belong to a technologically advanced race.

I also don't agree with us ultimatly destroying ourself, I think it would have to be an 'Act of God' so to speak to wipe us all totally out, I think we can become technologically advanced enough to re-colonise before such an event happens.

Coul you elaborate on what you mean by this? What is "technologically mature" with respect to this argument?

Technologically advanced enough to build such equipment/computers as described.

To add, it is not reasonable to think it is likely we are in a simulation. Explaining away our existence as an incredibly unlikely advanced species by presupposing the existence of an even more advanced species (or society) capable of simulating this world is a logical fallacy.

In that case, see my post above. Whilst we cannot rule it out, there is no reason to think such a scenario a reasonable possibility.

While the full simulation argument employs some probability theory and formalism, the gist of it can be understood in intuitive terms. Suppose that proposition (1) is false. Then a significant fraction of all species at our level of development eventually becomes technologically mature. Suppose, further, that (2) is false, too. Then some significant fraction of these species that have become technologically mature will use some portion of their computational resources to run computer simulations of minds like ours. But, as we saw earlier, the number of simulated minds that any such technologically mature civilisation could run is astronomically huge.

Therefore, if both (1) and (2) are false, there will be an astronomically huge number of simulated minds like ours. If we work out the numbers, we find that there would be vastly many more such simulated minds than there would be non-simulated minds running on organic brains. In other words, almost all minds like yours, having the kinds of experiences that you have, would be simulated rather than biological. Therefore, by a very weak principle of indifference, you would have to think that you are probably one of these simulated minds rather than one of the exceptional ones that are running on biological neurons.

So if you think that (1) and (2) are both false, you should accept (3). It is not coherent to reject all three propositions. In reality, we do not have much specific information to tell us which of the three propositions might be true. In this situation, it might be reasonable to distribute our credence roughly evenly between the three possibilities, giving each of them a substantial probability.

Let us consider the options in a little more detail. Possibility (1) is relatively straightforward. For example, maybe there is some highly dangerous technology that every sufficiently advanced civilization develops, and which then destroys them. Let us hope that this is not the case.

Possibility (2) requires that there is a strong convergence among all sufficiently advanced civilisations: almost none of them is interested in running computer simulations of minds like ours, and almost none of them contains any relatively wealthy individuals who are interested in doing that and are free to act on their desires. One can imagine various reasons that may lead some civilisations to forgo running simulations, but for (2) to obtain, virtually all civilisations would have to do that. If this were true, it would constitute an interesting constraint on the future evolution of advanced intelligent life.

The third possibility is the philosophically most intriguing. If (3) is correct, you are almost certainly now living in computer simulation that was created by some advanced civilisation. What kind of empirical implications would this have? How should it change the way you live your life?

Your first reaction might think that if (3) is true, then all bets are off, and that one would go crazy if one seriously thought that one was living in a simulation.

To reason thus would be an error. Even if we were in a simulation, the best way to predict what would happen next in our simulation is still the ordinary methods – extrapolation of past trends, scientific modelling, common sense and so on. To a first approximation, if you thought you were in a simulation, you should get on with your life in much the same way as if you were convinced that you are living a non-simulated life at the bottom level of reality.

The simulation hypothesis, however, may have some subtle effects on rational everyday behaviour. To the extent that you think that you understand the motives of the simulators, you can use that understanding to predict what will happen in the simulated world they created. If you think that there is a chance that the simulator of this world happens to be, say, a true-to-faith descendant of some contemporary Christian fundamentalist, you might conjecture that he or she has set up the simulation in such a way that the simulated beings will be rewarded or punished according to Christian moral criteria. An afterlife would, of course, be a real possibility for a simulated creature (who could either be continued in a different simulation after her death or even be “uploaded” into the simulator’s universe and perhaps be provided with an artificial body there). Your fate in that afterlife could be made to depend on how you behaved in your present simulated incarnation. Other possible reasons for running simulations include the artistic, scientific or recreational. In the absence of grounds for expecting one kind of simulation rather than another, however, we have to fall back on the ordinary empirical methods for getting about in the world.

If we are in a simulation, is it possible that we could know that for certain? If the simulators don’t want us to find out, we probably never will. But if they choose to reveal themselves, they could certainly do so. Maybe a window informing you of the fact would pop up in front of you, or maybe they would “upload” you into their world. Another event that would let us conclude with a very high degree of confidence that we are in a simulation is if we ever reach the point where we are about to switch on our own simulations. If we start running simulations, that would be very strong evidence against (1) and (2). That would leave us with only (3).

You shouldn't plagiarise other peoples' works without giving credit. And you shouldn't post such stuff without demonstrating you have, at least, some grasp of what you're posting. Just saying (IMG:http://media.profileheaven.com/images/style_emoticons/default/wink.gif)

On-topic, the theory is critiqued here:

"Before simply accepting it, it would be worthwhile to take a closer look at the formal probabilistic analysis that Bostrom asserts. I intend to argue here that Bostrom miscalculates the expected fraction of simulated people by ignoring the prior probabilities that are to be placed on the existence of such people.
....
The probability that at least one civilization reaches the ability to run simulations is equal to the probability that a civilization with the potential to reach such an ability exists times the probability that that civilization actually manages to reach the ability. This would be expressed as P(W)*[1-P(DOOM)], where W stands for the proposition that a world exists in which a civilization as the potential for achieving the ability to run ancestor simulations. Before, it was okay to assume that P(W)=1, because we know that at least one world (our own) exists with the possibility of running simulations someday. This allowed us to reduce the expectation of simulated people to [1-P(DOOM)]*N*H. However, because we can’t count our world towards the expectation of simulated people if we want to maintain the principle of indifference, the proposition W must become the proposition that a world other than our own exists in which a civilization has the potential for achieving the ability to run simulations.

Thus, the expectation of the number of simulated people becomes P(W)[1-P(DOOM | W)]*N*H. But, it is clear that the probability P(W) is simply the prior probability that we place on the existence of a world other than our own. If this probability is taken to be very small, then the conclusion of the simulation argument doesn’t follow, and we cannot conclude that it is probable that we are living in a computer simulation."

Tl;dr version: the theory assumes the probability of a civilisation reaching this level of technological maturity is 100%, but actually it's an unknown.

a chapter of a book i read a few months ago is on this (IMG:http://media.profileheaven.com/images/style_emoticons/default/laugh.gif)

if the universe is a multi-verse then chances are even if there is only a small miniscule fraction of these universes which can sustain life then the chances of living in a simulated universe (not just planet) are astronomically high. For the arguement is that for atleast one of teh civilisations that can do this will create a number of universes. of which are effectively real universes but living within a computer program. Many of tehse advances will be mistakes (eg a computer accidentally having to create us in order to work out a function). Then imagine the super-duper-mahoosive civilisations who have personal computers which have the power of a mini-universe (mini by their standards), the universe is infinite theory suggests this is likely if not probable

cant remember the technological terminology though (IMG:http://media.profileheaven.com/images/style_emoticons/default/sad.gif)

Some pretty big ifs in there old boy.

Edit: also the theory that the universe is infinitely big seems a complete non-sequitur to me/ If the Big Bang was an actual event, and time has only been flowing for a finite period of time, then the universe, expanding at the speed of light, is of finite size.

This post has been edited by DougieFFC: Mar 12 2010, 12:54 PM

cant remember the exact wording of the book, pretty convincing (not that i believe it) arguement was laid out. The multi-verse theory/different terrains (different regions of space time within our own universe where the laws as we know them are different) of our universe appears to be the most likely. Within this model, there are few universes/terrains that would be able to support life as we know it however seeing that this is an anthropomorphic view its not that bad an assumption that life or consciousness can exist outwith our understanding of it but we are still talking a miniscule number of universes/terrains in this one with the capacity to produce life as we know it. Now due to the size and make-up of our universe/terrain, it is very safe assumption that we are not the only life forms in this universe, some of which will be less advanced some of which will be more advanced (communication between our galaxy and the next are virtually impossible even in the most advanced possibilities according to our current models of the universe). This allows for a very safe 'if', one of these civilisations being advanced enough for a "universe computer" to exist. This would suggest minimum for each universe that can hold life, there is a secondary universe within said universe based in a computer. And (going to be anthropomorphic again) considering conscious life the way it is, you can never really have only one per species. Hell we have a number of different pyramids from civilisations which never met each other. Any rival factions on a planet will be quick to copy their rivals so this increases the number of "universe" computers. Even if no rivals exist, the tendancy for life to reproduce, and the tendancy for intelligent life to reproduce what it can, means these computers would become more powerful (bigger "universe" computers). This increases the ratio of computer universes against multi-verses


theres alot of 'if's as you say however none of them are in any way that far fetched and very easily arguable that its probable

one thing to remember: the population of the universe is 0. Simple mathmatics. lets say the universe is infinity - 1 just for arguements sake. within this there is infinity-2 number of planets, the minority of which have life on them. Take whatever life count you want but divide it by the size of the universe and turns out the people you see are just imaginary as the average population of the universe is 0 (douglas adams is a god)

as for your edit: completely agree with you, we only call it infinite because the human mind simply cannot fathom something as big as the universe

I wanted to see how long I could get people to argue against the point first (IMG:http://media.profileheaven.com/images/style_emoticons/default/laugh.gif) I never claimed it was my though. Head of psycology at Oxford i think who wrote it. (IMG:http://media.profileheaven.com/images/style_emoticons/default/unsure.gif)

The other threads in here are also plagiarised and written in first person (IMG:http://media.profileheaven.com/images/style_emoticons/default/lac.gif)

Hah. I believe Douglas Adams was just being delightfully absurd (there is no need to bring the number of planets in the universe into the calculation) (IMG:http://media.profileheaven.com/images/style_emoticons/default/laugh.gif)

If we are living in a computer simulation, whoever programmed my existence must have been having a bad day.

I'm going away to read up more and think about this before responding (IMG:http://media.profileheaven.com/images/style_emoticons/default/laugh.gif)

I liked the bit where he had the fight in the train station

For once I agree (IMG:http://media.profileheaven.com/images/style_emoticons/default/sad.gif)

*awaits you saying it's as reasonable as God* (IMG:http://media.profileheaven.com/images/style_emoticons/default/laugh.gif) (IMG:http://media.profileheaven.com/images/style_emoticons/default/sad.gif)