Try this physics paper[1] explaining how pretty much every model we have of physics is broken in fundamental ways. Things you take for granted because of what you've read in popular media (eg., heat death of the universe) are simply speculation based on stretching an incomplete mathematical model to its limits. The simulated reality nonsense is the same bad logic in a different guise.
Oh I've read it. It's a fun game to read through it and write down all the unfounded assumptions the author makes. It also doesn't help that his ideas about the complexity of the human brain are sorely outdated.
If you cannot convincingly argue the opposing side, then you have not thought hard enough about it. If you have no room for doubt, then there is no point discussing it. You have reduced science to zealotry. Don't waste my time.
You have already made it clear that you think his argument is undeniable. But since you insist on trolling, let me start with the obvious one.
In order to simulate a human brain, you need to simulate physics. Not a mathematical model of physics, but the actual true process that governs nature. In order to do that, you need to (1) understand the true laws of physics and (2) the process needs to be simulatable in polynomial time (at the very least). Where in the essay does he give you a convincing argument that these are true? Or is it just the lack of impossibility enough to convince you that they are possible?
The other poster is correct to say that simulating physics isn't actually needed, because Bostrom's argument depends only on ancestor simulations, not ancestor universe simulations. So simulating people doesn't require a) simulating physics, b) simulating the minutiae of brains.
Since these are post-humans, they understand the subtle interconnected algorithms implemented by human brains, and so can in principle bypass the need for low-level simulation. But even if that were not so:
> In order to simulate a human brain, you need to simulate physics. Not a mathematical model of physics, but the actual true process that governs nature.
You seem to be drawing some implicit distinction you find meaningful between "real" and "simulated", but this distinction isn't explained, and doesn't seem meaningful in any case.
> In order to do that, you need to (1) understand the true laws of physics and
The laws of physics needed for such simulations are sufficiently understood by post-humans, ie. for all physical observations simulated ancestors might make, posthumans understand physics far beyond that. So even without a perfect understanding of physics, they merely need to replicate the physics understood by their simulated ancestors.
> (2) the process needs to be simulatable in polynomial time (at the very least).
I don't see why. We already run non-polynomial simulations all the time (such as to solve fluid dynamics for aerodynamics, or climate models). As long as the results are expected to be useful, we will run them. This is actually a core premise driving Bostrom's argument: that ancestor simulations will be useful to future social sciences and such.
But all of this is neither here nor there, because Bostrom's argument is exhaustive. If there are legit reasons why post-humans cannot run such simulations, and there very well might be, he already covers this possibility as "we will go extinct before reaching the posthuman stage".
Like I said, Bostrom's argument is solid and there is no wiggle room. You get to choose one of the possibilities, for properly articulated reasons, and no more.
Bostrom does not define posthuman (so saying "no wiggle room" is ridiculous), so these conclusions about what posthumans understand and do not understand are unjustified and moot. But let me continue:
Bostrom assumes all simulated minds will be "of a similar sort." Another assumption that "minds" are well understood.
Bostrom assumes we will never have the means to glean any information related to whether or not we are in a simulation. Indeed, compared to the unprecedented assumptions needed to admit posthumanity (computers the size of planets, for one!), the assumption that we can determine whether we are in a simulation seems paltry by comparison.
Bostrom's indifference argument is unfounded. In particular, say I only give his proof a 1/N chance of being correct for a very large N. Then by his indifference principle I _still_ must assign an overwhelming probability that I am in a simulation. This doesn't help in that I cannot be 100% certain his argument is wrong since he does not define things rigorously enough for a proof, nor can he possibly do so because of our lack of understanding about human minds or the future of computation. So to be a "rational" being (I hate this term, because it's also undefined), I can't disagree with his argument and conclude the opposite of what he concludes.
You're making the unfounded assumption that it is necessary to simulate "the actual true process that governs nature"; Bostrom's argument does not require this, it only requires a simulation of people with our kind of experiences.
I don't think there is any requirement for a simulated universe to have any fully consistent laws of physics, let alone the 'true' laws (whatever they are - the laws imputed to hold in the universe in which the simulation is actually run?)
[1]: https://arxiv.org/abs/1609.01421