The simulation hypothesis, as it’s called, enjoys a certain popularity among people who like to think of themselves as intellectual, believing it speaks for their mental flexibility. Unfortunately it primarily speaks for their lacking knowledge of physics.
Among physicists, the simulation hypothesis is not popular and that’s for a good reason – we know that it is difficult to find consistent explanations for our observations. After all, finding consistent explanations is what we get paid to do.
Proclaiming that “the programmer did it” doesn’t only not explain anything - it teleports us back to the age of mythology. The simulation hypothesis annoys me because it intrudes on the terrain of physicists. It’s a bold claim about the laws of nature that however doesn’t pay any attention to what we know about the laws of nature.
First, to get it out of the way, there’s a trivial way in which the simulation hypothesis is correct: You could just interpret the presently accepted theories to mean that our universe computes the laws of nature. Then it’s tautologically true that we live in a computer simulation. It’s also a meaningless statement.
A stricter way to speak of the computational universe is to make more precise what is meant by ‘computing.’ You could say, for example, that the universe is made of bits and an algorithm encodes an ordered time-series which is executed on these bits. Good - but already we’re deep in the realm of physics.
If you try to build the universe from classical bits, you won’t get quantum effects, so forget about this – it doesn’t work. This might be somebody’s universe, maybe, but not ours. You either have to overthrow quantum mechanics (good luck), or you have to use qubits. [Note added for clarity: You might be able to get quantum mechanics from a classical, nonlocal approach, but nobody knows how to get quantum field theory from that.]
Even from qubits, however, nobody’s been able to recover the presently accepted fundamental theories – general relativity and the standard model of particle physics. The best attempt to date is that by Xiao-Gang Wen and collaborators, but they are still far away from getting back general relativity. It’s not easy.
Indeed, there are good reasons to believe it’s not possible. The idea that our universe is discretized clashes with observations because it runs into conflict with special relativity. The effects of violating the symmetries of special relativity aren’t necessarily small and have been looked for – and nothing’s been found.
For the purpose of this present post, the details don’t actually matter all that much. What’s more important is that these difficulties of getting the physics right are rarely even mentioned when it comes to the simulation hypothesis. Instead there’s some fog about how the programmer could prevent simulated brains from ever noticing contradictions, for example contradictions between discretization and special relativity.
But how does the programmer notice a simulated mind is about to notice contradictions and how does he or she manage to quickly fix the problem? If the programmer could predict in advance what the brain will investigate next, it would be pointless to run the simulation to begin with. So how does he or she know what are the consistent data to feed the artificial brain with when it decides to probe a specific hypothesis? Where does the data come from? The programmer could presumably get consistent data from their own environment, but then the brain wouldn’t live in a simulation.
It’s not that I believe it’s impossible to simulate a conscious mind with human-built ‘artificial’ networks – I don’t see why this should not be possible. I think, however, it is much harder than many future-optimists would like us to believe. Whatever the artificial brains will be made of, they won’t be any easier to copy and reproduce than human brains. They’ll be one-of-a-kind. They’ll be individuals.
It therefore seems implausible to me that we will soon be outnumbered by artificial intelligences with cognitive skills exceeding ours. More likely, we will see a future in which rich nations can afford raising one or two artificial consciousnesses and then consult them on questions of importance.
So, yes, I think artificial consciousness is on the horizon. I also think it’s possible to convince a mind with cognitive abilities comparable to that of humans that their environment is not what they believe it is. Easy enough to put the artificial brain in a metaphoric vat: If you don’t give it any input, it would never be any wiser. But that’s not the environment I experience and, if you read this, it’s not the environment you experience either. We have a lot of observations. And it’s not easy to consistently compute all the data we have.
Besides, if the reason you build an artificial intelligences is consultation, making them believe reality is not what it seems is about the last thing you’d want.
Hence, the first major problem with the simulation hypothesis is to consistently create all the data which we observe by any means other than the standard model and general relativity – because these are, for all we know, not compatible with the universe-as-a-computer.
Maybe you want to argue it is only you alone who is being simulated, and I am merely another part of the simulation. I’m quite sympathetic to this reincarnation of solipsism, for sometimes my best attempt of explaining the world is that it’s all an artifact of my subconscious nightmares. But the one-brain-only idea doesn’t work if you want to claim that it is likely we live in a computer simulation.
To claim it is likely we are simulated, the number of simulated conscious minds must vastly outnumber those of non-simulated minds. This means the programmer will have to create a lot of brains. Now, they could separately simulate all these brains and try to fake an environment with other brains for each, but that would be nonsensical. The computationally more efficient way to convince one brain that the other brains are “real” is to combine them in one simulation.
Then, however, you get simulated societies that, like ours, will set out to understand the laws that govern their environment to better use it. They will, in other words, do science. And now the programmer has a problem, because it must keep close track of exactly what all these artificial brains are trying to probe.
The programmer could of course just simulate the whole universe (or multiverse?) but that again doesn’t work for the simulation argument. Problem is, in this case it would have to be possible to encode a whole universe in part of another universe, and parts of the simulation would attempt to run their own simulation, and so on. This has the effect of attempting to reproduce the laws on shorter and shorter distance scales. That, too, isn’t compatible with what we know about the laws of nature. Sorry.
Stephen Wolfram (from Wolfram research) recently told John Horgan that:
- “[Maybe] down at the Planck scale we’d find a whole civilization that’s setting things up so our universe works the way it does.”
I cried a few tears over this.
The idea that the universe is self-similar and repeats on small scales – so that elementary particles are built of universes which again contain atoms and so on – seems to hold a great appeal for many. It’s another one of these nice ideas that work badly. Nobody’s ever been able to write down a consistent theory that achieves this – consistent both internally and with our observations. The best attempt I know of are limit cycles in theory space but to my knowledge that too doesn’t really work.
Again, however, the details don’t matter all that much – just take my word for it: It’s not easy to find a consistent theory for universes within atoms. What matters is the stunning display of ignorance – for not to mention arrogance –, demonstrated by the belief that for physics at the Planck scale anything goes. Hey, maybe there’s civilizations down there. Let’s make a TED talk about it next. For someone who, like me, actually works on Planck scale physics, this is pretty painful.
To be fair, in the interview, Wolfram also explains that he doesn’t believe in the simulation hypothesis, in the sense that there’s no programmer and no superior intelligence laughing at our attempts to pin down evidence for their existence. I get the impression he just likes the idea that the universe is a computer. (Note added: As a commenter points out, he likes the idea that the universe can be described as a computer.)
In summary, it isn’t easy to develop theories that explain the universe as we see it. Our presently best theories are the standard model and general relativity, and whatever other explanation you have for our observations must first be able to reproduce these theories’ achievements. “The programmer did it” isn’t science. It’s not even pseudoscience. It’s just words.
All this talk about how we might be living in a computer simulation pisses me off not because I’m afraid people will actually believe it. No, I think most people are much smarter than many self-declared intellectuals like to admit. Most readers will instead correctly conclude that today’s intelligencia is full of shit. And I can’t even blame them for it.