I'm yet to hear a simulation theory with more explanatory power than the much simpler theory of "God did it".
Most of the claims are variants of "but computers, so science", which is not an argument at all.
Most of the claims are variants of "but computers, so science", which is not an argument at all.
Given a universe with computational power P, you can simulate a "universe" of something like P * 10^-100. For example, a Minecraft world is a universe with different physical laws, in which you could perform even slower and worse simulations, and you can make "turtles all the way down" at lower and lower P.
The claim that our universe is not simulated, then, is nearly equal to the claim that the physical laws we have is the absolute highest P that could ever exist. Since we know we can simulate universes of much lower P than ours, we ought to have very good reason to assert that there is no universe of much higher P than ours. Given a finite speed of light in our universe, yet nonlocal effects (Bell inequalities) which appear to take instantaneous effect, we could perhaps fathom a universe of higher P created by having a method of communication which occurred instantaneously. Add to this more dimensions in time and space, etc... literally nothing is off the table for a "smarter" universe to be conceived of, because the containing universe's physical laws need bear no resemblance to our own.
Barring a literal divine intervention, though, it's all completely unfalsifiable, but I think it's more nuanced than "God did it".
In Minecraft, you can use redstone circuits to construct logic gates, and use those gates to build computational devices that are Turing-complete, in theory. But it's not possible to scale such devices up arbitrarily; you can build a simple CPU, but nothing that even approaches being able to run a nested copy of Minecraft. There are hard upper bounds on the amount of data that the simulation can cope with at once. (You can imagine patching Minecraft to allow keeping more chunks loaded at once, but you can't scale it up by very many orders of magnitude before you end up with something that can't run efficiently on any hardware that physically exists.)
Similarly, as Scott Aaronson describes in the article we're discussing, it's likely that there are finite bounds on how much computation can possibly be done before the heat death of our own universe. So it's fair to be skeptical that a tower of "turtles all the way down" could ever possibly exist, at least on a universal scale. If there's no tall hierarchy, then the anthropic argument (which says that we're unlikely to be at the top) breaks down.
You can certainly hypothesize higher levels which have infinitely fast communication, or other kinds of special properties that make deep simulations more feasible. (Greg Egan proposed one such cosmology in his novel Permutation City.) But you don't get to assume that and still use simulations within our own universe as examples, because you're talking about something entirely different.
What is "reasonable" to compute in a short amount of time in this universe has changed dramatically! For example, I want to prove the Goldbach conjecture. No problem! Just use this crazy computer to check every case, which is possible because this computer executes an infinite number of steps in two seconds.
Unfortunately [word choice?], in our universe such a computer needs an infinite amount of energy and would collapse into a black hole long before you received your answer!
'cogito, ergo sum'
We could very well be 'real' consciousnesses being fed artificial sensory data. While we would exist outside the simulation, our perception of objective reality might be fake.
I wonder why the machines made people live boring lives - seems like a great way to get them to wonder "is there more to life than this?"
When you say "God did it" - how did he do it?
The simulation idea often involves concepts like computers and turing completeness. Not sure those meet your idea of "explanatory" here. But they explain how it could be done. While I never saw an explanation how God did it.
I think Chalmers tries to introduce a kind of dualism here - he's saying that human experience is something special, unlike other mechanical processes (which can only be mere p-zombies). I don't think it is a good idea to turn to dualism because it has been proven flawed and leads to philosophical conundrums.
I think current day philosophy doesn't properly appreciate the insights coming from AI. We have seen AI give amazing results in perception : images, sounds, video - it's no mystery any more. You just put 100 layers deep convolutional nets to solve the problem from data. Philosophers still talk like we don't know how perception works, or that it results in ontologically special qualia.
Another very important AI insight that is being ignored by contemporary philosophers is Reinforcement Learning. We have made great advances in intelligent behavior, and RL concepts (agent, environment, reward, and learning) are better suited for explaining human consciousness than traditional concepts such as free will, qualia and Chinese Rooms.
Wittgenstein's concept of language games is apparent in reinforcement learning. There has been a recent paper about agents evolving a new language by trying to solve a problem together. Also, language philosophy should take a look at word embeddings.
Maybe philosophy needs more grounding in AI.
You're welcome to propose models that omit it, but they'll fail basic logic to me: they fail to explain the only experiment Im absolutely sure of the results of and which is continually running while I'm existing. Im less sure gravity exists than that qualia does for me.
It's entirely possible no one else does, or that they experience a different qualia. It's also not possible to prove that you do to others.
I see no point in trying to convince non-qualia-experiencing entities that I experience it, because they fundamentally don't have experiences and I don't think it's possible to bridge that gap.
I take the simulated Intelligence argument the same way. Suppose you could create a simulation of an intelligence that was indistinguishable from a real one? Well then, you'd have created an artificial intelligence. If such a thing reported that it experienced qualia I'd have no reason to doubt it.
Edit: to put it differently. Suppose I built a model of a Formula 1 engine. I used different materials at a different scale and used a different fuel, but to precise tolerances so that it could actually run. Would it be a Formula 1 engine? No. Would it be an internal combustion engine? Of course, nobody would doubt it.
Those arguments are very low-level in the intellectual stack, and can only address matters of subjective self because what they seek to establish or discuss is more fundamental than concepts like objectivity. (Well, cogito ergo sum is establishing an objective fact from a subjective one to give a basis for later objective discovery.)
Any full accounting of the world must explain the mechanism by which I experience it, or it hasn't explained the only part of the world Im sure exists (my experience of it), and hence can't be a full accounting. You can have a very good predictive model for features of that experience, but neglecting that experience -- qualia -- is leaving a major thing unexplained.
Similarly, cogito ergo sum is likely better phrased as "computation ergo existence" -- the process of doubting is a form of doing something, and so something must exist which is doing that (or is that process). This establishes that there must be some sort of existence, even if it's just a brain in a jar, random memory from quantum noise, etc. You can't doubt there's an existence, because the very act of doubting is proof of existing. You can only doubt the form of it.
I also disagree that we'd have no reason to doubt the claim, but I agree we have no a prior reason to reject it.
Your edit also makes a major assumption: that we know what causes qualia (our brain structure). That's the very thing being debated, so you're just begging the question.
As someone who has a pretty good grasp of both physics and computer science, I am personally convinced that there is no way a circuit board could give rise to the same type of subjective experience of qualia that I am experiencing. I know that's not really an argument, but just because I can't express my conviction in clearer terms doesn't make it any less real to me.
The problem is that when math doesn't gel its obvious that 2+2 doesn't equal 3 but with philosophy its entirely possible to become unglued from reality, further successive lifetimes of work may be built with no logical connection to underlying reality and no sanity check.
This is why philosophy majors should lay off the math and biology arguments.
In fact, the argument was refuted in print before Lucas ever published it, in a nice paper called "Minds and machines" by Hilary Putnam.
Exactly where it fails depends on exactly how it's stated, but here's a sketch:
Goedel proved that a formal system powerful enough to talk about mathematics either is inconsistent or else cannot prove its own consistency. Lucas and his followers claim that human mathematicians have no such limits; presented with such a system they can just see that it's consistent. In Lucas's version we look at some particular candidate system that might implement a human being, and just see it's consistent. In Penrose's version we look at mathematics as a whole and just know it's consistent.
But this is all nonsense. Real human mathematicians don't look at the sort of system that might implement a human being (still less, the totality of all mathematicians working together) and "just see" it's consistent. They don't even look at the nice streamlined formal systems they've made specifically for doing formalized mathematics in and "just see" that. Frege's system was inconsistent and he didn't notice after writing two volumes on it. (Russell famously pointed out an inconsistency.) Quine's ML was inconsistent and he didn't notice until Wang pointed it out. For all we know there might be some inconsistency lurking in ZF; it seems like a very good guess that there isn't, but that's all.
And, I repeat, those are highly streamlined systems that don't attempt to do anything nearly so complicated as describing the complete behaviour of an actual mathematician's mind.
We do sometimes attempt to study computer hardware and software -- systems a bit more like actual human minds, but still orders of magnitude simpler -- using formal methods. Sometimes we try to prove them correct. These proofs are also often wrong, which is why hardware and software have bugs. (In some cases we're pretty confident about relatively large systems; guess what?, the correctness proofs for those are done by computer and there's no "just seeing" about them.)
The idea that a human being could look at a formal system representing the entirety of what their brain does and "just know" that it's consistent is not just wrong, it's one of the wrongest things any otherwise intelligent human being has ever suggested. But that is (part of) what it would take to show that the formal system didn't really model them perfectly.
This is far from being the only major error in the Lucas-Penrose argument, but it's the worst one.