Manzotti and Smart recently published an article criticizing Nick Bostrom's "simulation argument" and Elon Musk's endorsement of it.
The simulation argument, basically, goes like this: the actual universe probably has lots of advanced civilizations. They are likely able to make simulations of worlds containing agents who think they are living in a real world. Because there is only one real world, and probably lots of simulated worlds, we are more likely to be living in one of the simulated ones than in the one real one.
The complete argument is, of course, longer and more detailed. You can read it here.
Manzotti and Smart (henceforth M&S) disagree, but present as fact is actually highly contentious in cognitive science, and mostly in disagreement with most cognitive scientists.
I'll present quotes from M&S's critique and talk about each one.
The notion that we may mistake a simulation of the world for the world is both conceptually and empirically flawed.
The obvious counterexample is dreaming. We already mistake simulations for reality, just about every night, and it's not even always that realistic. We're fooled anyway. M&S disagree...
But we have no idea whether dreams are like virtual reality simulation.
When I read this, I had to ask: if they are not like virtual reality (VR), then what on earth are they? They appear to be real but are simulated by our imaginations. That's a kind of virtual reality.
In fact, if, say, simulated water might be a meaningful notion, what would it be made of? It could not be made of real stuff, because if it was, it would no longer be simulated water. However, neither could it be made of simulated stuff, because—that’s the point of being a simulation—there is no such thing as simulated stuff. All we know is physical. All we know belongs, once again, to base reality. Either way, simulated water cannot exist.
What indeed is simulated water made of? If it's a computer simulation, then its physical instantiation would be computery-things, like voltage levels. So it's made of real stuff, so to speak. But this does not render it not simulated water, as M&S claim.
If the reality we see were a simulation, we should assume that the simulator is made of altogether different stuff that, by definition, we could not even conceive (it should be made of something completely different from everything we meet in our world). While the notion that there is a base reality and additional levels of reality is both appealing and enthralling, we have evidence of only one level of reality. The world we live in is just made of objects.
It's entirely possible that we are living in a simulation and that the real world looks a lot like the one we live in. It need not be inconceivable. We indeed have only evidence of one level of reality (with qualifications I'll get to), but we might say the same thing when we're in a dream. But dreams happen, and in the world of the dream there's no evidence of another level or reality, but there is another level of reality--the one with a brain creating the dream.
After all, this is confirmed by science itself, whose equations describe the flow and interactions of one kind of stuff—matter and energy according to relativity theory and quantum mechanics. No additional stuff appears in the scientific description of reality.
To say that the world we live in is just made of objects is contentious, too. Although at first blush it seems reasonable, we also speak of centers of gravity (which are made of neither mass nor energy), stories, points in football games, and lots of other things that are either not made of matter or the physical instantiation of them is not what's important about them. In fact, there is a popular theory in philosophy of science called "scientific realism," which holds that we should believe as real the theoretical entities in working scientific theories. And these include things not made of matter, like centers of gravity. I'm not saying that scientific realism is absolutely true, but M&S dismiss it out of hand. To say that our scientific description of reality contains nothing but matter and energy is clearly incorrect. If they were right, we'd be able to come up with physical descriptions of the following terms: phenotype, political revolution, GDP, extraversion, natural selection, Gaussian distributions, and stock fluctuations. We can't.
They also are dismissive of computationalism:
Very simply, this is the assumption in philosophy, cognitive science and AI that computations are sufficient for thought. Bostrom continues, “Suppose that these simulated people are conscious (as they would be if the simulations were sufficiently fine-grained and if a certain quite widely accepted position in the philosophy of mind is correct).” The “certain quite widely accepted position” is known as computationalism—which is the belief that consciousness is isomorphic with or caused by computations. It is nothing short of an article of faith, since we have no empirical evidence that computation, whatever it is, leads to conscious experience. Bostrom asks to believe that consciousness stems out of computational processes.
Yes, Bostrom does. And although there are many smart people who disagree with Bostrom on this point, they are in the minority. I'm not saying that computationalism is right because there is almost a consensus on the issue, I'm saying that it's still contentious and they dismiss it rather quickly. To wit:
Yet, we know that many scientists are very skeptical about the analogy between brains and computers.
Computationalism does not require that brains are like computers. Bostrom makes no claims about what might be creating the simulation--it might be a brain, and not something we would normally call a computer.
If a simulated waterfall is not wet, why should a simulated mind think or feel? A mind, unless one believes in disembodied souls, requires a brain, a body, and a world.
Let's take calculation. You can multiply 24 x 6. We can also do that on a computer or a calculator. Is the computer actually "calculating?" If a simulated waterfall is not wet, then why should a simulated mind calculate? Thinking is different from wetness in that, the way most cognitive scientists think of it, thinking is ultimately an information processing enterprise, and wetness is not. Again, most cognitive scientists might be wrong, but you should know that M&S hold the minority view.
They also take a cheap shot by suggesting that if we believe in minds that could run on a computer then we are like religious people who believe in souls. I don't believe in souls, but I believe that minds are complex processes that can arise in the machinations of many kinds of physical substrates: human brains, animal brains, and possibly alien or computer substrates that we can't imagine. Don't group me in with people who believe in heaven and hell over that.
A mind without a physical world is a myth. And a simulated world is a myth too. The fact is that all minds we know of, human minds and possibly animal minds, are embodied and situated: they have a body and they partake of the physical world. We have never met a disembodied mind. We always meet bodies in the world.
Nobody's saying that the simulated minds aren't running on some physical hardware, be it a brain or a computer. So it's not a mind "without a physical world." The physical world is what the simulation is running in (possibly a computer of some kind), but the apparent physical world that the mind is experiencing would be a simulation.
I can imagine M&S hundreds of years ago, talking about the impossibility of non-biological calculation: "The fact is that all calculation we know of, that of human minds, are embodies and situated: they have a body and partake of the physical world. We have never encountered disembodied calculation. We always meet bodies in the world."
In conclusion, I'm not saying that M&S are wrong. I do want to say that their position is a legitimate but minority view in cognitive science.