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Presumably the redness of red is VERY hard to communicate fully brain to brain because the experience of it is dependent upon every input and computation before that point however we manage to do it well enough.

Its like saying that some deficits in computability prevent us us from doing arithmetic and therefore from launching rockets successfully at distant targets.

I might never know the exact pattern in my brain of the "redness of red" as experienced by you but it seemed to work well enough for my brain to form a pattern similar enough to communicate thoughts just as the incompleteness or inherent lack of precision of measurement don't prevent the rocket from being launched successfully.

The issue is not whether we can pragmatically communicate the concept of "red" by piggybacking on some (presumed) common experience, but whether that experience of redness itself is information. It is obviously not, and I do not understand why you insist otherwise.

Making up something you can't define and then describing the thing you invented as uniquely human is a bad argument.

This idea boils down to if you believe the human brain exists purely in physical space. Let's assume it does. There is no free will. Every thought, every neuron, every sense can be represented and is controlled solely by energy and matter. We could record the electrical signals between your optic nerve and your brain, and send those same signals to your brain again in the future. We could recreate what you perceive as red by shocking your brain in the right place at the right time. If we perfectly understood the human brain, the sensation of red would be defined as a sequence of neurons that need to be turned on and off at the right time.

As far as I know, the only thing limiting us from perfectly understanding the brain is our limitations with measuring it. I don't know of any scientific studies that claim the brain exists outside of physical space.

Let's assume the brain doesn't exist purely in physical space. Free will exists. There is something immeasurable and outside of matter and energy that experiences the color red. Sensations are impossible to define because they exist only in this immeasurable world.

I heard about a guy that claimed it was obvious that the origin of lightning and earthquakes were from the gods themselves. I try not to think like that guy.

> If we perfectly understood the human brain, the sensation of red would be defined as a sequence of neurons that need to be turned on and off at the right time.

A sequence of neurons firing is not equivalent to the sensation of red. It doesn't even tell you anything about the nature of the sensation of colour more broadly, or why the sensation of red looks the way it does and not like, say, the sensation of blue or yellow instead.

All you have is a material correlate -- a merely descriptive physical "law".

> A sequence of neurons firing is not equivalent to the sensation of red.

Have you seen videos where people perform experiments on people's brains while they're awake? The subjects experience sensations that are inseparable from their neurons firing.

I would say the sensation of red and neurons firing are the exact same thing to the person experiencing it. It's like saying a flashlight that is on is different than photons traveling away from a light bulb with a battery and a current. They're the same thing to the observer. The sensation of red is caused by and is only possible by neurons firing. The neurons firing causes and only results in the sensation of red. The observer does not know the difference.

> It doesn't even tell you anything about the nature of the sensation of colour more broadly

I don't think seeing red tells us about the sensation of color more broadly either. I think that's a concept created through human discussion, not by our senses.

> or why the sensation of red looks the way it does and not like, say, the sensation of blue or yellow instead.

I was talking to your point of "but whether that experience of redness itself is information". I don't know why red looks the way it does, but I imagine the reason exists in the physical world and we could find out if we understood the brain.

I do think in the future we could activate someone's neurons and have them experience red, blue, and yellow in any combination we want. And we could give someone else the same experience (hypothetically we perfectly understand the brain) by activating neurons in their brain. I think that is perfectly communicating color.

> The subjects experience sensations that are inseparable from their neurons firing.

What does "inseparable" mean? That the sensation occurs at the same time that the neurons fire? That may be true, but it doesn't make them equivalent.

> It's like saying a flashlight that is on is different than photons traveling away from a light bulb with a battery and a current.

They're not the same, for what it's worth. The term "flashlight" conveys a certain intent and structure that "photons traveling away from a light bulb with a battery and a current" does not.

> The sensation of red is caused by and is only possible by neurons firing. The neurons firing causes and only results in the sensation of red. The observer does not know the difference.

The fact that two different phenomena are closely coupled via a cause and effect relationship does not make them the same phenomena.

If you push two magnets together, the fact that the same force causes them to attract or repel does not mean that the motion of the first is literally equivalent to the motion of the second, or that the force itself is literally equivalent to either motion. They are closely correlated, but ultimately distinct.

You just can't avoid the fact that qualitative phenomena do exist in their own right. They can't be explained away using a physical model that assumes from the get go that they don't exist.

Erwin Schrodinger said:

> Scientific theories serve to facilitate the survey of our observations and experimental findings. Every scientist knows how difficult it is to remember a moderately extended group of facts, before at least some primitive theoretical picture about them has been shaped. It is therefore small wonder, and by no means to be blamed on the authors of original papers or of text-books, that after a reasonably coherent theory has been formed, they do not describe the bare facts they have found or wish to convey to the reader, but clothe them in the terminology of that theory or theories. This procedure, while very useful for our remembering the facts in a well-ordered pattern, tends to obliterate the distinction between the actual observations and the theory arisen from them. And since the former always are of some sensual quality, theories are easily thought to account for sensual qualities; which, of course, they never do.

> What does "inseparable" mean? That the sensation occurs at the same time that the neurons fire? That may be true, but it doesn't make them equivalent.

Can a sensation exist without neurons firing? The root of our conversation is the question if a sensation purely exists in the physical world. If it does, then it is possible to measure it. If it doesn't, then that breaks our scientific understanding of the world and would be exciting news.

> They're not the same, for what it's worth. The term "flashlight" conveys a certain intent and structure that "photons traveling away from a light bulb with a battery and a current" does not.

Yes there is no strict definition of a flashlight. Let's use your definition of a flashlight. Is it possible in your mind to separate the concept of a flashlight and your definition? Without "your definition here", the flashlight no longer exists. My point was without firing neurons, the sensation does not exist.

> The fact that two different phenomena are closely coupled via a cause and effect relationship does not make them the same phenomena.

My wording was not the best. My point was that the sensation of red is physically equivalent to neurons firing. How do we measure a sensation? If we cannot measure a sensation, does it exist in the physical world? If it doesn't exist in the physical world, then what does it existence mean to the scientific community?

> If you push two magnets together, the fact that the same force causes them to attract or repel does not mean that the motion of the first is literally equivalent to the motion of the second, or that the force itself is literally equivalent to either motion. They are closely correlated, but ultimately distinct.

I agree that these forces are distinct. We can measure the force of each magnet separately and we can define the motion of one magnet without referencing the motion of the other.

> You just can't avoid the fact that qualitative phenomena do exist in their own right. They can't be explained away using a physical model that assumes from the get go that they don't exist.

What is a qualitative phenomena? I couldn't find information on this term.

If we can't measure a qualitative phenomena in the physical space, what does it mean to exist?

These discussions are normally expositions of how the other party misunderstands reality and or terminology with a dash of if i don't understand it but can vaguely describe it then it must be inexplicable.

I agree. I am also not cut out to be a philosopher.

Scott Aaronson has, iirc, suggested the idea that the complexity of such an isomorphism could be the distinguishing thing between whether or not something should be said to be computing a particular think. Sounds plausible to me.

Why should the complexity matter, so long as the computation is recognizable as such?

It's possible create an interpretation where all of the computation happens in the interpreter instead of the system being interpreted.

With the right algorithm, could interpret the randomly moving particles in a gas as computing conway's game of life or anything else, if the algorithm just disregards everything about the particles and contains instructions that generate the expected results from conway's game of life. In that extreme case, I don't think it's useful at all to claim that the gas particles are simulating conway's game of life.

In an opposite extreme, you could say that the randomly moving particles in a gas are computing the motion of the random movements of particles in a gas. The interpretation algorithm is just "look at the particles at time t. Their locations represent the particles' locations at time t.". It's clear here that the system being interpreted is in fact doing all the computation and that nothing is hidden in the interpreter's work.

One interesting way to try to differentiate these two cases is that if you want the results of a longer-running simulation, then in the latter case, you let the actual system run longer, and the work to interpret it doesn't increase at all. In the former case, if you want to get the results of running conway's game of life for 2000 steps instead of 1000 steps, then it doesn't matter how long you let the gas particles go on for, but you do have to do more work on the interpreting side.

I believe that if you could prove that you have an actual isomorphism in the full formal sense of the world, the question about its complexity wouldn't really matter.

However, for a practical claim, it is probably impossible to formally prove that an interpreter function is both bijective between a physical system and a computation (it maps absolutely every possible state of the physical system to exactly one step of a computation).

However, it's important that the following argument can be made: if the evolution of a physical system is isomorphic to a computation of a particular algorithm for solving the traveling salesman problem, and if the phsyical system needs ~1 second for each step, then the system can't go from state A to state B in less than X seconds, where X is the number of steps required by that algorithm to reach those same steps. The actual interpretation of the algorithm or its purpose is not relevant here, the mathematical limits of how the computation happens remain relevant regardless.

That is because you can't find 2 different isomorphisms between the same physical system and 2 different computation that are not isomorphic to each other, if these are actual proper isomorhpisms (bijective) and not just hand-wavy analogies.

> I think you're missing the central point, which is that computation is observer relative. Anything can be interpreted as a computational process.

This is completely wrong. The opposite is true: computation is a mechanical process, it does not depend on an observer giving it meaning. It's true that the same mechanical process can be interpreted as different computations, but they will have the exact same computational properties (e.g. complexity), only the result will be interpreted differently.

In particular, it is extremely unlikely that the wall is implementing Word Star, because WordStar is a highly structured computation. The wall MIGHT be implementing some very simple additions, and essentially any process is implementing any one step computation.

> I think you're missing the central point, which is that computation is observer relative. Anything can be interpreted as a computational process.

I see what you're saying, and maybe I am misunderstanding your point, but to me it seems like you've gotten yourself bogged down in wordplay when there is something much simpler going on: say I have a human named Bob from Des Moines, and next to him is a machine constructed to approximate Bob to arbitrary accuracy (this is possible because Bob is a made up of a finite number of particles/wavefunctions). Are you arguing that there's something special about Human Bob? If so, what is your argument for that? The two are "indistinguishable" and by that I mean whatever threshold you have for two things to be "indistinguishable" (practically speaking), you can technically make a reproduction of Bob that satisfies that threshold.

> That's circular reasoning. The point is that qualia are not something which, in principle, can be the subject of computation. There is no way to represent the fullness of sensation itself, like the redness of red or the softness of silk, as information. So how can our brains be "computing" it?

I would argue this is circular reasoning. "There is no way to represent the fullness of sensation itself" -- yes I would argue there is: whatever time-dependent set of physical states make up this "realization" in your brain.