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ArisKatsaris comments on Rationality Quotes: April 2011 - Less Wrong
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Not quite. What I'm saying is there might be a difference between the computation of a thing and the thing itself. It's basically an argument against the inevitability of Tegmark IV.
A Turing machine can certainly compute everything there is to know about lifting rocks and their effects -- but it still can't lift a rock. Likewise a Turing machine could perhaps compute everything there was to know about consciousness and its effects -- but perhaps it still couldn't actually produce one.
Or at least I've not been convinced that it's a logical impossibility for it to be otherwise; nor that I should consider it my preferred possibility that consciousness is solely computation, nothing else.
Wouldn't the same reasoning mean that all physical processes have to be solely computation? So it's not just "a Turing machine can produce consciousness", but "a Turing machine can produce a new physical universe", and therefore "Yeah, Turing Machines can lift real rocks, though it's real rocks in a subordinate real universe, not in ours".
I think you mean, it's the skeleton of an argument you could advance if there turned out to actually be some meaning to the phrase "difference between the computation of a thing and the thing itself".
Herein lies the error: it's not up to anybody else to convince you it's logically impossible, it's up to you to show that you're even describing something coherent in the first place.
Really, this is another LW-solved philosophical problem; you just have to grok the quantum physics sequence, in addition to the meanings-of-words one: when you understand that physics itself is a machine, it dissolves the question of what "simulation" or "computation" mean in this context. That is, you'll realize that the only reason you can even ask the question is because you're confusing the labels in your mind with real things.
Could you point to the concrete articles that supposedly dissolve this question? I find the question of what "computation" means as still very much open, and the source of a whole lot of confusion. This is best seen when people attempt to define what constitutes "real" computation as opposed to mere table lookups, replays, state machines implemented by random physical processes, etc.
Needless to say, this situation doesn't give one the license to jump into mysticism triumphantly. However, as I noted in a recent thread, I observe an unpleasant tendency on LW to use the notions of "computation," "algorithms," etc. as semantic stop signs, considering how ill-understood they presently are.
Please note that I did not say the sequence explains "computation"; merely that it dissolves the illusion the intuitive notion of a meaningful distinction between a "computation" or "simulation" and "reality".
In particular, an intuitive understanding that people are made of interchangeable particles and nothing else, dissolves the question of "what happens if somebody makes a simulation of you?" in the same way that it dissolves "what happens if there are two copies of you... which one's the real one?"
That is, the intuitive notion that there's something "special" about the "original" or "un-simulated" you is incoherent, because the identity of entities is an unreal concept existing only in human brains' representation of reality, rather than in reality itself.
The QM sequence demonstrates this; it does not, AFAIR, attempt to rigorously define "computation", however.
Those sound like similarly confused notions to me -- i.e., tree-sound-hearing questions, rather than meaningful ones. I would therefore refer such questions to the "usage of words" sequence, especially "How an Algorithm Feels From The Inside" (which was my personal source of intuitions about such confusions).
Fair enough, though I can't consider these explanations as settled until the notion of "computation" itself is fully clarified. I haven't read the entire corpus of sequences, though I think I've read most of the articles relevant for these questions, and what I've seen of the attempts there to deal with the question of what precisely constitutes "computation" is, in my opinion, far from satisfactory. Further non-trivial insight is definitely still needed there.
Personally, I would more look for someone asking that question to show what isn't "computation". That is, the word itself seems rather meaningless, outside of its practical utility (i.e. "have you done that computation yet?"). Trying to pin it down in some absolute sense strikes me as a definitional argument... i.e., one where you should first be asking, "Why do I care what computation is?", and then defining it to suit your purpose, or using an alternate term for greater precision.
You say it has a practical utility, and yet you call it meaningless? If rationality is about winning, how can something with practical utility be meaningless?
Here's what I mean by computation: The handling of concepts and symbolic representations of concepts and mathematical abstractions in such a way that they return a causally derived result. What isn't computation? Pretty much everything else. I don't call gravity a computation, I call it a phenomenon. Because gravity doesn't act on symbolisms and abstractions (like numbers), it acts on real things. A division or a multiplication is a computation, because it acts on numbers. A computation is a map, not a territory, same way that numbers are a map, not a territory.
What I don't know is what you mean by "physics is a machine". For that statement to be meaningful you'd have to explain what would it mean for physics not to be a machine. If you mean that physics is deterministic and causal, then sure. If you mean that physics is a computation, then I'll say no, you've not yet proven to me that the bottom layer of reality is about mathematical concepts playing with themselves.
That's the Tegmark IV hypothesis, and it's NOT a solved issue, not by a long shot.
A computer (a real one, like a laptop) also acts on real things. For example if it has a hard drive, then as it writes to the hard drive it is modifying the surface of the platters. A computer (a real one) can be understood as operating on abstractions. For example, you might spell-check a text - which describes what it is doing as an operation on an abstraction, since the text itself is an abstraction. A text is an abstraction rather than a physical object because you could take the very same same text and write it to the hard drive, or hold it in memory, or print it out, thereby realizing the same abstract thing - the text - in three distinct physical ways. In summary the same computer activity can be described as an operation on an abstraction - such as spell-checking a text - or as an action on a real thing - such as modifying the physical state of the memory.
So the question is whether gravity can be understood as operating on abstractions. Since a computer such as a laptop, which is acting on real, physical things, can also be understood as operating on abstractions, then I see no obvious barrier to understanding gravity as operating on abstractions.
This is similar to my point, but the other way around, sort of.
My point is that the "abstraction" exists only in the eye of the observer (mind of the commentator?), rather than having any independent existence.
In reality, there is no computer, just atoms. No "computation", just movement. It is we as observers who label these things to be happening, or not happening, and argue about what labels we should apply to them.
None of this is a problem, until somebody gets to the question of whether something really is the "right" label to apply, only usually they phrase it in the form of whether something can "really" be something else.
But what's actually meant is, "is this the right label to apply in our minds?", and if they'd simply notice that the question is not about reality, but their categorization of arbitrarily-chosen chunks of reality, they'd stop being confused and arguing nonsense.
If computation isn't the real thing, only the movement is, then a simulation (which is the complete representation of a thing using a different movement which can however be seen as performing the same computation) is not the thing itself, and you have no reason to believe that the phenomenon of consciousness can be internally experienced in a computer simulation, that an algorithm can feel anything from the inside. Because the "inside" and the "outside" are themselves just labels we use.
The question of qualia and subjective experience isn't a mere "confusion".
Of course, which is why the entirety of the existence of a real computer is beyond that of a mere Turing machine. As it can, for example, fall and hurt someone's legs.
Yes, which is why there's a difference between the computation (the map) and the physical operation (the territory). A computer has an undisputed physical reality and performed undisputed physical acts (the territory). These can be understood as performing computations. (a map). The two are different, and therefore the computation is different from the phsycail operation.
And yet, pjeby argues that to think the two are different (the computation from the physical operation) is mere "confusion". It's not confusion, it's the frigging difference between map and territory!
My question is about whether gravity can be fully understood as only operating on abstractions. As real computers can't be fully understood as that, then it's the same barrier the two have.
It is possible to have more than one map of a given territory. You can have a street map, but also a topographical map. Similarly, a given physical operation can be understood in more than one way, as performing more than one computation. One class of computation is simulation. The physical world (the whole world) can be understood as performing a simulation of a physical world. Whereas only a small part of the laptop is directly involved in spell-checking a text document, the whole laptop, in fact the whole physical world, is directly involved in the simulation.
The computation "spell checking a text" is different from the physical operation. This is easy to prove. For example, had the text been stored in a different place in physical memory then the same computation ("spell checking a text") could still be performed. There need not be any difference in the computation - for example, the resulting corrected text might be exactly the same regardless of where in memory it is stored. But what about the simulation? If so much as one molecule were removed from the laptop, then the simulation would be a different simulation. We easily proved that the computation "spell checking a text" is different from the physical operation, but we were unable to extend this to proving that the computation "simulating a physical world" is different from the physical operation.
As a sidenote, whenever I try to explain my position I get downvoted some more. Are these downvotes for mere disagreement, or is there something else that the downvoter objects to?
Not quite. The Tegmark IV hypothesis is that all possible computations exist as universes. This is considerably more controversial than what pjeby said, which was only that the universe we happen to be in is a computation.
Um, no, actually, because I wouldn't make such a silly statement. (Heck, I don't even claim to be able to define "computation"!)
All I said was that trying to differentiate "real" and "just a computation" doesn't make any sense at all. I'm urging the dissolution of that question as nonsensical, rather than trying to answer it.
Basically, it's the sort of question that only arises because of how the algorithm feels from the inside, not because it has any relationship to the universe outside of human brains.
If a computation can be a universe, and a universe a computation, then you're 90% of the way to Tegmark IV anyway.
The Tegmark IV hypothesis is a conjunction of "the universe is a computation" and "every computation exists as a universe with some weighting function". The latter part is much more surprising, so accepting the first part does not get you 90% of the way to proving the conjunction.
Actually, what pjeby said was that it was meaningless outside of its practical utility. He didn't say it was meaningless inside of its practical utility.
My point stands: Only meaningful concepts have a practical utility.
I just explained why your point is a straw man.