David Deutsch’s New Theory of Reality | Hacker News Reader

David Deutsch’s New Theory of Reality

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43 pointsghosh15 comments

Pretty much gibberish. No operational definitions, lots of floating abstractions, with some falsehoods thrown in (starting with the description of Shannon as obscure!)

Deutsch is a very clever guy, but to say "no one but a fool would bet against the notion that something could become important" is vacuous as well as pompous. I could become Pope--you cant prove I won't--but that is hardly a bet worth taking.

Laws that govern laws are interesting, and symmetries that require information conservation would also be interesting, and in fact the paper in question (http://arxiv.org/ftp/arxiv/papers/1405/1405.5563.pdf) looks interesting. The write-up unfortunately is not.

He describes Shannon as 'unsung' not 'obscure' and I think there's some validity to that. I grew up reading about the incredible scientific developments - especially on the theoretical side - that happened throughout the 20th century and Shannon's name was often mentioned but it was always in passing (and sometimes with a subtle hint that he didn't really grasp how broadly applicable his ideas were). It wasn't until I read about his life and work directly that I learnt that this picture was rather inaccurate.

Is there a particular book/biography on Shannon you'd recommend? I've not found anything that looked particularly definitive.

I can't for the life of me remember what it was I read now. I thought it might have been David Deutsch's 'Fabric of Reality' or some similar bit of broad, sweeping, pop-science but I can't find my copy right now to check. (However that's a great book if you want a bluffer's guide to Popper ;-)

I'm sure the journalist in question who should learn not to write gibberish, ensure he's inserted his operational definitions and check his prose for floating abstractions is properly put to rights! I guess you weren't referring to the actual paper since it can hardly turn out to be interesting and gibberish at one and the same time.

Since both outcomes are possible, by following the constructor principle, the paper will be in a superimposed quantum state of interesting at gibberish.

And it will collapse in one of those states when somebody (knowledgeable in the field) reads it.

EDIT: the analogy is broken on purpose, to cause a logical paradox

>The conservation of energy is not a mathematical truth

http://en.wikipedia.org/wiki/Noether%27s_theorem

"...every continuous symmetry of a physical theory has an associated conserved quantity; if the theory's symmetry is time invariance then the conserved quantity is called "energy" ...".

Looks like a poor rewording of something from the paper, where it basically says that conservation of energy is a consequence of the laws of motion instead of an assumption:

> In the theory we present here, the status of information in physics is analogous to that of (say) energy: given the laws of motion of physical objects, neither the concept of energy nor the conservation law for the energy-momentum tensor are necessary for making any prediction from initial data, yet our understanding of the physical world would be radically incomplete without them. The conservation law explains some aspects of motion as consequences of a deeper regularity in nature – which is why we expect as-yet-undiscovered laws of motion to conserve the energy-momentum tensor too; but we don’t expect to derive new laws of motion from it. It is a principle – a law of physics that constrains other laws rather than the behaviour of physical objects directly.

Furthermore he says "Thus the conservation law, though not an a priori mathematical truth, provides [...]".

Imho "not [...] a priori" is not the same as a simple "not".

Haven't read the paper or anything, just judging that quote out of context:

I think it's folly to try to differentiate a "law" from a "principle". That said I'm taking his words out of context. He's saying that "information" is something akin to "energy". Ok, but after the hand-waving there is nothing left.

Does he say something more interesting? For example, we've explored many truths about "computation" (e.g. Turing's Halting Problem && Godel's Incompleteness Theorem) that so far have only been discussed in the abstract. But to weave computation/information onto physics raises questions of how these truths we've held in the abstract may also correspond to laws in the physical. That is, it doesn't help us derive new laws of physics (in other words, our laws of physics is always incomplete), but constrains what can be explained by laws (which by definition must be consistent).

TLDR; I agree that information doesn't exist in the abstract but is tied to our physical reality. I think that our inability to find a complete set of laws of the physical universe is intimately related to HP and GIT. I wonder if he gets into it.

IANAP but it's kind of fun to try to read the start of the PDF, it doesn't seem to require much advanced math.

But information is not abstract in the same sense as, say, the set of all prime numbers, for it only exists when it is physically instantiated.

This seems to be an important point to Deutsch, but it doesn't seem completely obvious to me. E.g. I can reason about the effects of purely hypothetical information which in fact does not exist.

I am not a quantum physicist by training, trade, or hobby, but I did do some level of dabbling in information theory some time back.

This appears to be than a restating of aspects of information theory, with extensions to quantum information. Is that something heretofore lacking?

I believe that this would be about information diffusion in some kind of quantum field

Whatever the answer to that question is, you will not be able to determine it from that article, which is little more than a pointer to the existence of a theory, and one keyword from that theory, left all-but-entirely undefined.

I read/skimmed the article (not the linked article, the actual PDF), trying to deduce the novel contributions that were not already reformulations.

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