On 19 Jan 2014, at 04:05, meekerdb wrote:

On 1/18/2014 1:09 AM, LizR wrote:
On 18 January 2014 19:51, meekerdb <meeke...@verizon.net> wrote:
On 1/17/2014 10:18 PM, LizR wrote:
On 18 January 2014 19:12, meekerdb <meeke...@verizon.net> wrote:
But where does it exist? X has to be conscious of a location, a physics, etc. If all this is the same as where I exist, then it is just a translation of this world into arithmetic. It's the flip side of "A perfect description of X is the same as X", i.e. "X is the perfect description of X". If every perfect description is realized somewhere in arithmetic (and I think it probably is) nothing is gained by saying we may be in arithmetic.

Don't we gain less entities, making Occam a bit happier? If we can get the appearance of a universe without having to actually have one, can't we "retire the universe" and just stick with the "appearance-of-one-with-equal-explanatory-value" ? (Not an original idea, of course, I'm fairly sure Max Tegmark said something along those lines regarding his mathematical universe hypothesis -- that if the maths was isomorphic to the universe, why bother to assume the universe was physically there?).

I'm asking why have the maths?

Well (putting on my AR hat) we have it because the maths is necessarily existent, while the universe isn't.

I disagree. The maths are necessarily true, i.e. "axioms imply theorems" is true.


But why should that imply *existence*.

It does not. Unless we believe in the axioms, which is the case for elementary arithmetic. But then we believe in the existence of prime numbers, and in the many relative computational states.

We know we can invent all kinds of maths by just changing the axioms or even changing the rules of inference.

OK. But note that we don't do that for arithmetic, except by adding axioms, or using another theory.

Sometimes people on this list post the semi-mystic opinion that everything=nothing, pointing to the need for discrimination. I look at this as saying positing everything is the same as saying nothing.

I agree. But searching a theory, we have to define the things first. then in some theory the "nothing" can appear to be already Turing complete, so that in that frame, the nothing theory get incarnated. In classical physics you need at least three bodies to get Turing universality.
In quantum mechanics the vacuum is already Turing complete. For example.

Of course there's an answer - we can manipulate the maths - but then doesn't that proves that the maths aren't the universe. They wouldn't be any use as predictive and descriptive tools if they WERE the things described. They are only useful because they are abstractions, i.e. they leave stuff out (like existence?).

Well .... the maths does have that "unreasonable effectiveness" (that you're probably bored to death hearing about). And one reason for that could be because it is - in the guise of some yet-to-be-discovered TOE - isomorphic to the universe.

Or it could be because we, denizens of this physics/universe, invent them.

But that's the case we have to explained why they work or seem top work, it seems to me.



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