On 29 Nov 2017, at 20:45, Brent Meeker wrote:



On 11/29/2017 2:27 AM, Bruno Marchal wrote:

On 28 Nov 2017, at 14:52, Jason Resch wrote:



On Tue, Nov 28, 2017 at 7:50 AM, Jason Resch <jasonre...@gmail.com> wrote:


On Tue, Nov 28, 2017 at 6:06 AM, Bruno Marchal <marc...@ulb.ac.be> wrote:

On 27 Nov 2017, at 04:04, Jason Resch wrote:


Richard Feynman in "The Character of Physical Law" Chapter 2 wrote:

"It always bothers me that according to the laws as we understand them today, it takes a computing machine an infinite number of logical operations to figure out what goes on in no matter how tiny a region of space, and no matter how tiny a region of time. How can all that be going on in that tiny space? Why should it take an infinite amount of logic to figure out what one tiny piece of space/time is going to do?"

Does computationalism provide the answer to this question,

Yes.    :)



Very nice. It seems then Feynman's intuition was in the right place. The second half of the above quote was:

"So I have often made the hypothesis ultimately physics will not require a mathematical statement, that in the end the machinery will be revealed and the laws will turn out to be simple, like the checker board with all its apparent complexities. But this is just speculation."

So it looks like that simple machinery is the machinery of the universal machine and the simple laws are those of Peano (or Robinson?) Arithmetic.


in the sense that even the tiniest region of space is the result of an infinity of computations going through an observer's mind state as it observes the tiniest region of space?

That might be OK, if space was something entirely physical, which is suggested by the physics of the vacuum, or general relativity, but with Mechanism, spece and time might be less physical than here suggested. The reason is that it is not clear how "empty space" could make a computation different from another,

I think what I was thinking here were "closed loop feyman diagrams", where any possible diagram might be drawn in the tiniest area of space, so long as it is closed, e.g. fluctuations/ particle creations are permitted so long as they all cancel out. So if space is physical, and enables any of these fluctuations to happen, then this noise can take any possible value from the observer's point of view (like the polarization of a photon).

and so space could be only a marker differentiating some computations, like time seems to be in the indexical approach. All this would need big advance in the mathematics of the intelligible and sensible arithmetical matter. I expect space to be explained by quantum knot invariant algebra due to subtil relation between BDB and DBD logical operators (I mean []<>[] and <>[]<>). Kant might be right on this, apparently space and time are really in the "categorie de l'entendement", I don't know Kant in English sorry, but this means mainly that they belong to the mind).


Thanks I very much appreciate these additional insights. I do subscribe to the belief that time is an illusion created by the mind. I have a little more trouble seeing that when extended to spacetime as a whole. Though perhaps what's come closest to helping me see this picture is Amanda Gefter's excellent book "Trespassing on Einstein's Lawn"--I would recommend it to everyone on the Everything list. It takes the approach that only things that are invariant are real, and from there proceeds to deconstruct almost all of physics.

Jason


I wanted to add, it also shows that the function (if you can call it that) of practically every physical law is to ensure consistency between observers. I think you would like it.


That is needed to have first person plural realities, but truth is also very useful. "just consistency" is good for multi-user video game, but the truth requires sound proposition,

What does "sound" mean?

In our context, a theory T is sound if its theorems are true in the standard model of arithmetic. i.e. when (T proves A) -> [ (N, 0, +, *) satisfies A].




"True" is not definable in logic.

Truth about a first order logic theory is definable in second-order logic, or in set theory. Set theoretical truth is not definable in ZF, but is definable in ZF + kappa. Truth theory is a vast sub-branch of mathematical logic.





ISTM it's just a marker "t" for the rules of inference, i.e. those transformations that preserve "t". Without empiricism or something like it "t" has no interpretation.

Don't confuse the constant boolean t, which in our context can be interpreted by 1 = 1, and the predicate "true", which by incompleteness (à-la Tarski) needs a richer theory to be defined. We use such richer theory all the times in many part of science, no need to do "bad philosophy". truth is not a problem when handled with some caution.

Bruno



Brent

and consistency is too cheap (PA + []f is consistent), that is why we need both nuances: []p & <>t and []p & <>t & p.

So yes, I like what you say, and it is the main motivation for the Z1* logic ("intelligible matter", []p & <>t), but the X1* logic (sensible matter, []p & <>t & p) requires some notion of Truth/God/ One.

Bruno



Jason


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