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pjeby comments on Rationality Quotes: April 2011 - Less Wrong
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Comments (384)
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".
You keep using that word "is", but I don't think it means what you think it means. ;-)
Try making your beliefs pay rent: what differences do you expect to observe in reality, between different states of this "is"?
That is, what different predictions will you make, based on "is" or "is not" in your statement?
Consider that one carefully, before you continue.
Really? Would you care to explain what differences you predict to see in the world, as a result of the existence or non-existence of these concepts?
I don't see that we have need of such convoluted hypotheses, when the simpler explanation is merely that our neural architecture more closely resembles Eliezer's Network B, than Network A... which is a very modest hypothesis indeed, since Network B has many evolutionary advantages compared to Network A.
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.
I interpret it more as an (attempted) dissolution of "existing as a universe" to "being a computation". That is, it should be possible to fully describe the claims made by Tegmark IV without using the words "exist", "real", etc., and it should furthermore be possible to take the question "Why does this particular computation I'm in exist as a universe?" and unpack it into cleanly-separated confusion and tautology.
So I wouldn't take it as saying much more than "there's nothing you can say about 'existence' that isn't ultimately about some fact about some computation" (or, I'd prefer to say, some fixed structure, about which there could be any number of fixed computations). More concretely, if this universe is as non-magical as it appears to be, then the fact that I think I exist or that the universe exists is causally completely determined by concrete facts about the internal content of this universe; even if this universe didn't "exist", then as long as someone in another universe had a fixed description of this universe (e.g. a program sufficient to compute it with arbitrary precision), they could write a program that calculated the answer to the question "Does ata think she exists?" pointed at their description of this universe (and whatever information would be needed to locate this copy of me, etc.), and the answer would be "Yes", for exactly the same reasons that the answer is in fact "Yes" in this universe.
So it seems that whether this universe exists has nothing to do with whether or not we think it does, in which case it's probably purely epiphenomenal. (This reminds me a lot of the GAZP and zombie arguments in general.)
I'm actually having a hard time imagining how that could not be true, so I'm in trouble if it isn't. I'm also in trouble if it is, being that the 'weighting function' aspect is indeed still baffling me.
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.
My point is that I don't know what is meant by something being meaningless "outside of its practical utility". Can you give me an example of a concept that is meaningful outside of its practical utility?