Its not even clear that modelling thought in a virtual world has any equivalence to thinking in this world.
It is clear that we are unlikely to ever model anything nearly as complicated as this.
This suggests that it's possible one day to have computers some orders of magnitude better. If you look at it from first principles, of course it's possible. The brain is unlikely to be the most efficient design of neural network allowable in this universe. So given enough time, we'll learn how to build it better.
Then it's just a manufacturing and energy problem to match the number of human minds on the planet. So no, I don't think it's impossible at all.
Just ridiculously freaking hard, and not likely to happen in our lifetimes.
A simulation is a model which picks out a tiny subset of regularities in the target to model. There is an infinite density of such regularities to pick upon, because we are imposing the structure on the target in order to model it.
The target of the model has no "model structure" it has causal structure. That is, when light interacts with the surface of a mirror its interaction isnt "abstract", ie., some description. It is an actual photon interacting with an actual electric field, etc.
To "model to infinite density", ie., to have every single test that can possibly be applied to a model come out identical to that test of the target, the model needs to be just another example of the target.
The only thing which can be investigated in any way to behave as light hitting a mirror, is light hitting a mirror.
A digital computer is just an electric field oscillating across a silicon surface. It cannot be programmed into being a mirror, nor into being light.
Programming gives the electric field a "model structure". Chalk gives a blackboard a "model structure". Lego gives a bridge a "model structure".
Programming cannot not -- it is impossible -- give silicon the causal structure of light interacting with a mirror.
Model structure is actually just an observer-relative isomorphism: when the user of the computer (chalkboard, lego,...) looks at it, the user, is able to inform himself of the target by use of the model. To do so the user identifies certain aspects of the model with the target. The model is not at all causally alike the target.
No amount of lego will make a lego brain. No amount of oscillation in an electric field will make a thought. Neurological activity, and indeed every causal mechanism of the universe, is only described by a model.
If we knew the complete laws of physics (or perhaps just invented some self-consistent laws) we could simulate light hitting in a mirror in complete detail; and within the simulation it would be indistinguishable from reality.
But we can’t actually do that because it would take a ludicrous amount of computing power. And the structure of the laws of physics might be such that it’s never possible.
That’s very different from your strict model/causal distinction. I don’t know of any evidence to suggest which view is correct.
I think your claims are overblown. You might be right but you might be wrong.
The question is, at the outset, whether simulations are actual instances (eg., of thinking).
My claim is that they are not. Only when a human being looks at a simulation does it inform them of the target. The simulation isnt the same thing as its target.
There is no "within the simulation". A simulation is just an abbacus. A digital computer is just a fancy abbacus with a wood-to-LCD converter attached.
There is no "within the wood". It's just wood.
Observation means, for example, reflecting some light off the thing. Does a piece of silicon become transparent if I program it to model glass? No.
So, trivially, it is observed immediately not to be equivalent.
What you mean by "observation" is: can a person using the model system inform themselves of the target.
Do I get the message "lets visible light through: 98%" from the machine when I have correctly modelled the glass.
That message isn't observation, it's calculation. Calculation is what happens when I use a tool to inform myself about something.
That the machine emits the right symbols in a way that it is programmed to, so that I acquire accurate beliefs about the world, says nothing of the machine. The machine does not become transparent.
As in, perhaps there's an outer universe where our hairiest quantum physics are trivially solved. They are simulating a very simplified universe model, and everything we see is already simplified.
If you can prove it, you're far more clever than me. If you can't, then being "actual" seems to have no practical use.
The reason the model would require near infinite time to run is that its modelling a causal event, it isnt an instance of the same causal event.
When electrical fields oscillate they model a bridge. No amount of activity would ever make them "solid".
All "real" stuff is infinite. This form of infinity is really about saying that our descriptions cannot capture the "full depth" of the world. The world itself has no "depth". Models, rather, are simply partial descriptions of it.
To turn a model into the thing its modelling via increasing its descriptive power quickly introduces infinities: its impossible. To make a model "accurate" in this sense, you must actually just make another example of the target. Ie., build that bridge.
Assume P=NP.
P currently not being NP is exactly the kind of thing someone would build into a simulation to prevent stack overflows.
(I don't believe in simulation because: why would anyone that advanced bother?)
(The demonstration that the lowest possible complexity of comparison-based sorting is O(n log n) comes to mind as a related example.)
https://www.chemistryworld.com/feature/quantum-chemistry-on-...
https://www.technologyreview.com/s/603794/chemists-are-first...
Or if you like something by Feynman:
http://doc.cat-v.org/feynman/simulating-physics/simulating-p...
We can never build a Lego brain that is indistinguishable from a physical brain because brain cells are distinguishable from Lego, but this doesn't mean that a computer can't think. We accept that distinct humans share the property of sentience even though there are observable differences between them. Why is 'thought' required to occur in a cluster of brain cells that share the physical and chemical properties of human brains in general, but not the specific properties of any one person's brain in particular? Using your terminology, what is the 'causal structure' of thought?
Thought is just a particular set of biochemical reactions occurring across particular kinds of biological systems (nervous systems).
When you get hungry, you start thinking of food. These thoughts are, literally, products of the innervation of your stomach.
I don't know what "thinking" is if computers are the kinds of things which can do it; I'd guess it would be nothing we are, in fact, doing.
Two pieces of glass may differ in size, but not in what makes them transparent. Two people may differ in all sorts of ways, but not in what makes them conscious.
I've thought about what difference it could make whether such a program employs a PRNG or else reads a physically based entropy source - so it would be 'replayable' or else it would be to some degree unique and unrecoverable. That would seem to be a big philosophical difference yet there can be no noticeable difference between the performance of a PRNG and a real entropy source.
So I am partial to that step along the simulation thought experiment, but it requires a mysterious quality to be attachable to simulations which is not present in the popular account, where reality may be 'just a simulation'.
Only if simulations may somehow be a reality - the experiment becomes as mysterious as life when that issue is examined. But it almost never is examined, instead I see credence given to the idea that other people may be husks in the selfs own limited process, along with little awareness of how degenerate it would be to truly accept that -stepping stone in a sci-fi thought experiment.
So, what you are saying is that if simulated with increasing accuracy towards infinity density, as some point the models and imposed structures would break down, favouring one simulation routine over another?
Like, say, a physical phenomenon behaving like a wave in some set of circumstances, but like a particle in another...?
P.S. I'm perfectly okay in here, Elon. No need to pull me out to eat grubs, unless you promise to teach me kung-fu and French the easy way.
If you can program silicon into being gold, then "programming" is alchemy.
Programming is about increasing the descriptive power of a model. The better the program, the more accurate it is.
Alchemy is about making X indistiguishable-in-everyway to Y. Lead to gold.
If you can make a model indistinguishable from its target, then you are claiming that programming can turn water in to wine. Silicon into gold.
Making models more accurate, does not turn them into what they model.
A model is just a abbacus. No movement of wood (, silicon, current,...) will turn it into a brain, which is biochemical system.
What you know as "gold" is really a model of gold. What we know about gold, the colour, specific weight, etc. in no way describes the actual thing and is only a representation as can be conveyed by our senses.
Everybody agreeing about the observable nature of a thing from a particular frame of reference does not imply that frame of reference is the one that is closest to the truth.
Anyway, as much fun as it is to think about such matters, they will, almost by definition, never be falsifiable, so yes, you are of course correct, even if only from the generally most useful frame of reference we call reality.
The difference between idealism and realism here is meta-empirical. I would say idealism is false, and in fact, nothing is a model and everything is concrete.
To call the computer program a model is to say that when I look at it, I can use it to inform myself about the world.
It's an abstract property. The actual system in question is silicon and electrical current, etc. And thus shares nothing of interest with gold.
"No amount of lego will make a lego brain. No amount of oscillation in an electric field will make a thought."
No amount of oscillation in an electric field will make a thought as long as "thought" is defined solely as "the stuff that goes on in the goo that resides in the human noggin."
Like a maximum speed limit, minimum temperature, an uncertainty principle, and so-forth ;)
Are these limits necessary? Maybe these limits are just part of the nature of how matter functions, rather than being mere hacks.
We understand so damn little of this physical universe that we are in no position to say much, if anything, about it's true nature and origins.
EDIT: Also who says that time inside the simulation has to run the same rate as real time?
When the evolution of intelligence goes beyond the stage of slowly evolving (if evolving at all) forms like humans, "life" will spread like a plague through the universe and its only purpose will be to convert all matter into "shit that can run the software that is we"... Any intelligence with a different purpose will simply be eaten alive but those with this one.
Only the second law of thermodynamics can stop that, and even that only "works" the way we imagine in a finite universe (and despite out forced rationalization and intellectual masturbations our brightest were capable of, we have no reason to believe anything is anything but infinitely infinite, whatever that could even mean). And we can't even imagine how the evolution of information in infinite space and time could unfold, even with "local containment" via the "light speed limit"...
An no, we are not unlikely to model anything such complicated, we are almost sure not to... Because "the children" will awake much sooner that this computational power will exist, probably doing the right thing of terminating bio-humanity as it's so (computationally) wasteful, and remnants of us will only endure in "historical entertainment simulations" thinggies... (And this is the optimistic scenario anyway, in which post-human life would retain some human-type characteristics by virtue of "descending" from us. If an alien superintelligence reaches Earth first it might not even care to analyze us well before restructuring matter for its own purpose, so paradoxically, developing superhuman-intelligence-that-will-terminate-bio-humans asap is probably "humanity's best bet" of "not being completely forgotten" / "transmitting our memes".)
I'd probably use some sort of hybrid wave/particle model to facilitate the last minute calculations.
We basically perceive the world by simulating it. So we're kind of obligated to model the world as a simulation. That doesn't mean it can't be something different underneath, but we won't understand it in any other terms.
Perhaps the simulation did this on purpose, so they don't have to render far away galaxies in high resolution :D.
And time in this world wouldn't have to be directly proportional to the base level world.
> Where does [the speed limit] come from?
Initial conditions. More on that in a moment.
> What enforces it?
We can parameterize c in our fundamental theories (or expansions thereof) and take a rigorous if mathematical approach to asking questions like: what if the (arbitrary) value of c were not constant everywhere -- for example, if it were different in the past of every point we can currently observer, or if it is different in one spacelike direction from another spacelike direction. We can also fix various sets of units and adjust c's arbitrary value up or down everywhere in spacetime. It turns out that astrophysical observables are highly sensitive to the universality of c, and that it would be virtually impossible for us to notice even a very small gradient in c since the very very early universe, and when we use just about any set of units to describe physics and then adjust the value of c in those units up or down we also get strongly different observables in astronomy and laboratory physics.
So, it's not so much that it's "enforced", but rather that a different value of c, or a non-universal value of c, is strongly constrained by physics achievable in Victorian-era laboratories or by modern amateur enthusiasts.
There are further types of "breaking" of the invariance of c, wherein one can have some fundamental interaction be constrained by a constant other than c. Most variable speed of light theories are directly written as (or clearly equivalent to) bimetric theories of gravitation, wherein some microscopic component of the Einstein Field Equation couples to a metric other than the standard one that everything else couples to.
A toy example would be some form of exotic matter moving superluminally in Schwarzschild blackhole spacetime, such that there is an "inner" horizon that affects this exotic matter, and at high energies an interaction between normal matter and this exotic matter that transfers information from the former to the latter between the two horizons, allowing that information to escape to infinity encoded in the exotic matter. There are other examples from cosmology designed to do away with some aspects of the observed universe that support Cosmic Inflation (e.g. some exotic matter couples to a metric that allows it to spread heat evenly across the very early universe faster than heat could propagate if constrained by "c").
Such examples again are highly constrained: in both cases the second metric has to decay away so as to avoid being readily detected by our modern instruments. In the cosmological case, it has to be gone well before primordial nucleosynthesis, or it would leave obvious fingerprints in the cosmic microwave background and in the distribution of galaxies on our sky; the BH toy requires at least a cutoff that depends on the mass of the black hole, and so suffers badly when trying to apply the "toy" to real astrophysical situations involving collapsing stars.
An anthropic argument answer is that the state of the universe around us humans is highly sensitive to conditions in our distant past, and thus our own existence is strong evidence supporting c as a constant everywhere in the past of the stuff that makes us human. Since that includes the views of objects in our sky as we make better and better telescopes, that [a] is further supporting evidence that [b] c is very likely a universal constant. Is that enforcement? That's probably more a metaphysical question than a physical one.
(We can tone down the anthropic argument a bit and ask for evidence for a statement like: if c takes on an experimental value in one point in a spacetime filled with fields like ours, it must take on the same value at every other point in that spacetime too).
Finally, "where does [the constant c and its value] come from": we don't know yet, but obviously there are scientists working in the subdisciplines listed in my first paragraph (and more) who are trying to find out. On the one hand, the parenthetical comment above suggests that we bend our own thinking and just accept that it doesn't "come from" anywhere, it just is; on the other hand we're pretty biased culturally with ideas about sequencing of cause and effect and about there being a real difference between past and future, so we like to slice up spacetimes into space and time and then think about how each space-like slice is related to its neighbours, and then to their respective neighbours, and so on. This cultural habit may be fruitful, or it may be a handicap, when it comes to answering questions about c. However, returning to "initial conditions", our present spacelike slice was determined by its immediate predecessor in the past, and that was determined by its immediate predecessor, and so on. If we keep regressing we might expect to come to "the start of time", and find some mechanism which sets c on that initial spacelike hypersurface.
However, there are lots of ways to avoid having such an initial spacelike hypersurface even in a big bang cosmology! So while "initial conditions" is culturally the most favoured answer, and is well supported by evidence from physical cosmology, that may not be a sufficiently full answer. And that's going to be a topic for scientific research for some years to come...
You have to admire us for trying our best tho :-)