Sir Martin Rees, Royal Society professor of astronomy at Cambridge University, agrees that it is now possible to conceive of computers so powerful that future societies may use them to build an entire virtual universe. In fact, like Nick Bostrom (who penned the first academic treatise on the subject), Rees wonders if we ourselves aren't the inhabitants of such a simulation.
These types of futuristic proclamations are nothing new for Rees, who has also argued that humans will eventually spawn machine intelligences and develop molecular assembling nanotechnology. It looks to me like he's keeping himself up to speed on all the transhumanist literature.
Now, on a related note, I'd like to take issue with a claim made by Jonathan Leek, the author of the Times Online article about Rees (which is really quite weak). In the article, "Top scientist asks: is life all just a dream?", Leek writes that René Descartes "famously came down in favour of existence, saying: 'I think, therefore I am.'" He uses this as possible evidence in favour of the argument that we are not in a simulation.
This is not an accurate interpretation of Descartes's assertion, nor does it disprove the Simulation Argument. In fact, Descartes's dictum opened the door to the possibility that existence as it is perceived may be a complete fabrication of some sort. Cartesian skepticism suggests that the only thing we can know for certain is that we can be aware of our own conscious, subjective self.
Further, a simulated reality would still constitute a bona fide 'existence' that could be experienced by a self-referential agent. I believe Leek is suggesting the contrary. A simulated existence is still an existence so long as it is perceived by a conscious observer and a high degree of modal realism is maintained.
This isn't the first time that Martin Rees has weighed in about the world as a simulation theory. See, for example, this 2003 piece from
the Edge. Thanks anyway for the heads up about the program. Do you know when and where it will be on in North America? Will there be an online link to it somewhere? I'd be very interested in watching it to see if he touches on any of the issues in my recent paper on historical simulations.
Hah, the idea that 'I think, therefore I am' invalidates the Simulation Argument is beyond silly - the unfortunate fact of the matter is that less than 1% of the population accepts causal functionalism, and the rest find the idea of a mind in a computer impossible. Anyway, when I read this post and came across that line, I thought "what an amazing cop-out!"
Another case where someone famous comes around to a way of thinking which has been obvious to many for a long time.
I have occasionally played around in various online simulated worlds, beginning with a program called ActiveWorlds in about 1997. Even before then I'd read sci-fis such as Neuromancer and Snow Crash (which I believe was the inspiration to create the ActiveWorlds program). Also when I was a kid early 3D games such as Elite gave the impression of being in a large simulated universe. Now we have more modern simulated environments such as There or Second Life, and I think these will become even more realistic and increasingly popular in the years and decades ahead.
Recent announcements about future CPUs having tens or hundreds of cores, including GPUs, lead me to believe that within another decade it will be possible to produce 3D simulated environments which are so compelling that it will be hard to discriminate between a simulated experience and a video of a real location.
I'm not necessarily a fan of the theory, though it certainly makes a good thought experiment. That said, I agree that the error about Descartes (in The Times) is pretty bad.
Descartes concludes that "I am, I exist" whenever I think about it - based on the impossibility of contemplating otherwise (though the exact structure of the argument remains controversial). Even the possibility that I am being deceived about everything else by an evil demon presupposes that I do actually exist to be deceived, so Descartes reasons. As far as it goes, this argument - along with the fact of his own existence as a "thinking thing" - is totally compatible with the evil demon hypothesis.
To reject the demon hypothesis, Descartes has to go on to prove the existing of a non-deceiving God. Most philosophers believe his attempted proofs fail.
All that said, I don't actually think that modal realism has anything to do with it. The argument is not about possible worlds in David Lewis's sense. Even if we are in a simulation, we are part of the actual, realised, world; our thoughts and perceptions supervene on whatever physical substrate is actual.
Hence, there's no need to buy into modal realism to accept the simulation argument. If the argument has a weakness, it isn't anything as straightforward as its reliance on the controversial theory of modal realism.
I would agree with the comment of Russell Blackford above me, and the comments of your main article. But I don't think Martin Rees is making any philosophical comment about existence (he's into physics, not philosophy). He's just making a general comment that an advanced human civilisation would be able to simulate us, and we'd have no idea. That's basically all he's saying. You're right - the criticism in the Times was wide of the mark.
I consider the Simulation Argument in my own blog: http://www.ipod.org.uk/reality/reality_big_brother.asp
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