On 5/14/2012 4:29 AM, Bruno Marchal wrote:


On 13 May 2012, at 23:19, Evgenii Rudnyi wrote:

On 13.05.2012 15:09 Bruno Marchal said the following:

On 12 May 2012, at 14:59, Evgenii Rudnyi wrote:

On 12.05.2012 13:33 Bruno Marchal said the following:
Evgenii,

All this is well known. Copenhagen theory, or "unique-universe" theory
are non computationalist dualist theories.
But as Shimony has shown, the idea that consciousness collapse the wave leads to many difficulties, like non local hidden variables in physics, or solipsism in philosophy of mind. Or even just the problem to say what
exactly is the collapse, on which all believers in collapse differ.

Computationalism and Everett (QM without collapse) have no problems in
that respect, and line up well with the everything-like use of Occam.


I listen currently to Beginning of Infinity by David Deutsch. Yet, I
am not convinced that Multiverse is a good explanation.

The multiverse is a logical consequence of "1+1= 2", and mechanism. You
don't need quantum mechanics.

Then quantum mechanics, the first theory in physics succeeding to
survive more that 5 years (indeed about a century now), is very solid,
and based on very simple math, and it confirms the mechanism
multiverse/multidream.

So, to avoid the multiverse, you have to postulate very special physical
laws, yet unobserved, and a very special theory of person, yet
unobserved. Why not, but it is very speculative, and seems to be driven
by wishful thinking only.

I am glad that you believe in multiverse and find it logical.

I am just saying that a "multiverse" or a "multidream" is a logical consequence of comp. Not that I believe in multiverse. But yes, it is plausible, and simpler conceptually than the speculation about one universe, or one computation.




Yet, I guess that even not all physicists believe in multiverse. When you convince all physicists that multivers exists, I will start thinking about it.

On reality, usually all humans are wrong. Also, if people start reasoning when the majority is convinced, this means that no one reason really. You should avoid that kind of authoritative argument. Science is not a question of majority vote.



For example, I do not remember that multiverse has been even mentioned in The Elegant Universe by Brian Greene. He discusses an eleven-dimensional space needed for the superstring theory but not the multiverse.

Martin Gardner said that the "many worlds" concept was the best hidden secret of the 20th centunary (and he talked of the QM multiverse, not the "more obvious" comp one).




You could as well defend the theory that the earth is flat, and build ad
hoc rules to explain why it seems to be a sphere.



I personally consider quantum mechanics just as a model.

Yes. It is a theory. An hypothesis, very weird, but strongly supported
by the facts, and whose main weird consequences are also a consequence
of elementary arithmetic, and mechanism (even without any facts).



David Deutsch does not like it, he says that instrumentalism is a bad
philosophy and that we must take physical theories literally.

I agree with Deutsch on this. That is science. Taking ideas seriously,
so that we can change the theories more quickly when refuted. But then
Deutsch uses comp, and very typically, like many, ignore its logical
consequence. So Deutsch does not follow his own philosophy.




In general, I am disappointed by his book. His style, "I know the
truth as this is a good explanation" is far away from skeptical inquiry.

After all, we know that quantum mechanics and general relativity
contradict to each other. Why then to invest too much time into
interpretations like Multiverse? Why it is useful?

To learn and to try to figure out what happens here and now.

Let us take chemists. They use molecular modeling for a long time and I would say they have been already successful without a multiverse.

No, this is false. They use multiverse all the time. They prefer to talk with the "superposition state labeling", and they can invent for themselves the idea that QM does not apply to them, to avoid the contagion of he superposition state, but that's word play to avoid looking at what happens. It is just avoiding facts to sustain personal conviction. Humans does that all the time. QM = multiverse. The collapse of the wave is already an invention to hide the multiverse, and it has never work.


Do you mean that when all chemists accept the multiverse interpretation, they will start working more productively?

They accept it. I have a book, by Baggot, who explains that he taught chemistry for 17 years, absolutely convinced that QM was true only on little distance, so he predicts that nature did not violate Bell's inequality, but when the experience of Aspect was done, he revised his opinion, and accept the idea that QM might be true macroscopically, and that it makes the weirdness a real fact of life. De Broglie behaves like ghat too. This illustrates that people can use a theory, without taking it seriously, because they follow their wishful conviction. It is typical for humans to do that.

If you decide the destination of your holiday with a quantum choice, QM predicts that all the term of the wave makes sense, and that "you" will differentiate into going to all the chosen Holiday places. If you believe that only one term "really results", it is up to you to say what is wrong in QM.

Hi Bruno,

Could we agree that this concept of "really results" is merely the folk language way of talking about what we can communicate unambiguously about? I see this as the same kind of idea as what you describe with Diary entries in your UDA. In that sense it seems to me that this is something that could use more closer exploration. I have a conjecture that our "shared reality" is restricted to being representable by a Boolean algebra (not a Heyting algebra!), have you any comment on this? (I suspect that I am missing something in this conjecture but am not sure what it is.)



Now, physicists never define what they mean by universe, with comp, we could say that there is zero universes, indeed, zero physical objects, we are dreaming those things, the universes are first person plural construct.

This concept of "first person plural" is something that I have never understood. Could you elaborate on it please?

The "matrix" image is more close to reality than a substantial reality, and this, by comp, explains where the physical reality comes from. To have a unique real universe, you need a non computationalist theory of mind, and nobody even try to present one.

I agree with you here, but my reasoning is different. A non-computationalist theory of mind does not have to be one that denies that the specific content of _any singl_e experience (1-p) is Turing emulable, it could be a theory that shows how a _sequence_ of 1-p content is not Turing computable without accounting for the specific means that the resources for the computation became available.


The weakening of the comp hypothesis does not suppress any "universes/dreams", on the contrary.

I agree, but it does severely undermine the idea that the mere existence and a priori truth of formal sentences uniquely determines the content of those sentences. A good analogy to this is seen in Shannon's theory of information <http://en.wikipedia.org/wiki/Information_theory>; there is nothing that quantifies the particular meaningfulness of a message in the theory. It is only about the ability to recognize a signal as distinct from noise. This is the difference between a statistical notion and a non-statistical notion.


--
Onward!

Stephen

"Nature, to be commanded, must be obeyed."
~ Francis Bacon

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