Bohr and solipsism

computerphys

I wonder if Bohr QM point of view could be labeled as "solipsism" or even "Metaphysical solipsism". Any hint would be appreciated.

I may be wrong at some point, so I would be glad to hear other opinions or corrections.

According to Bohr (subjective Copenhagen interpretation of Quantum theory) "there is no underlying reality".

I have also heard another softer version: "we are unable to describe reality between measurements", but that would be to say that QM is unable to describe reality and that would be equivalent to say that QM is incomplete (Einstein's point of view). I would be very surprised to discover that Bohr stated such a thing!

So, I think only hard version "there is no underlying reality" could be really Bohr's world view. Right?

If that is true, can we say that Bohr was a solipsist? According to Wikipedia, Metaphysical solipsism is an idealism based on the argument that no reality exists other than one's own mind. I think that is quite the same as to say that "there is no underlying reality", isn't it?

Thanks in advance for any other point of view.

kote

Good question, but Bohr was definitely not a solipsist . Bohr has often been misinterpreted through the various versions of the "Copenhagen Interpretation" over many years. I recommend reading http://plato.stanford.edu/entries/qm-copenhagen/. From the article:I also highly recommend reading Bohr's "Atomic Theory and the Description of Nature." Don't trust second hand sources when it comes to historic QM interpretation (But Jan Faye of the SEP article is good). Original Bohr is very readable.

To get more into your question... Bohr definitely believed that QM was complete, while also believing that we can't describe reality between measurements. But asking what happens between measurements didn't make sense for Bohr. From ATDN:Any underlying "real essence" for Bohr is and has always been outside of the scope of physics or descriptive language. He argues for this conclusion from relativity:So Bohr isn't a solipsist and he isn't denying that anything exists. He's saying that we had the wrong idea all along. It was never about an objective description of things "out there." What are measurements or any events except for interactions? And how do you have interactions without your observee and observer - how do you have any events at all with no context for them to occur in?

It relates to the "If a tree falls in a forest..." question. Bohr would say that a tree falling in a forest does not make a sound if no one is there to hear it. Sound is not a thing that exists independently of ears. It takes both a falling tree and a working set of ears with a brain attached for sound to exist. It also requires proper experimental conditions - the tree cannot be in a vacuum etc. But without ears, a falling tree only creates vibrations in the air.

All phenomena, for Bohr, require a measurement context to exist. Everything, in this sense, is subjective. But this is not something new to QM. This is a simple epistemological fact. That is why Bohr can say that QM is complete. There is no way around the problem, quantum uncertainty or not, so the best thing we can do is accept it and move on.

GeorgCantor

Yes.



I'd say he was.


"Everything we call real is made of things that cannot be regarded as real."

-Niels Bohr

computerphys

Let's apply some logic to that: if a complete theory can't describe reality between measurements then reality becomes indescribable there, right?

So, reality is indescribable. If you say something is indescribable, isn't that describing it? Reductio ad absurdum.

If you find anything wrong in this reasoning, please tell me.

Thanks again.

JoeDawg

No, that is not a description, any more than x is a description for 3.14...

Its merely a placeholder.

The word 'nothing' is similar. Linguistically, nothing, is a noun, which as you may know, is a person, place or thing.

The word 'nothing' is really just a negation of 'thing', as in 'no-thing', but since language is abstract, and can treat concepts as things, the lack of a thing can be treated as a thing.

Language is flexible... and in a lot of cases it is the nature of language that has caused a lot of confusion in philosophy.

And no, Bohr is not a solipsist. But people use the word 'reality' to describe different things.

apeiron

If you know there to be actually something, then already you are describing "something", even if the details are sparse. So claiming something to be literally indescribable is simply self-contradictory here.

And as for the gaps between measurements, again you know there to be gaps that are "really there". QM gives you a description of what can fill those gaps - even if the sum over histories allows an exact degree of uncertainty.

The quantum zeno effect would be relevant here. Making the gaps between measurements smaller has an interesting result on reality.

http://en.wikipedia.org/wiki/Quantum_Zeno_effect

skippy1729

Solipsism can never be proved or disproved. Since Bohr never openly advocated solipsism, your question really is:

Can Bohr's theory be consistent with a rejection of solipsism.

********************

1. Assume the existence of minds other than your own; Alice and Bob.

2. Alice and Bob prepare identical classical apparatus to measure spin or something. They record and plot their results. Their individual results will be different but they will (within experimental error) both be representable by the same probability distribution.

3. That the probability distributions are the same is evidence of an underlying objective quantum reality even though the properties of individual quantum "particles" do not have pre-existing values (i.e. are not real).

Therefore rejection of solipsism is consistent with Bohr's theory.

"There is no underlying reality." does not imply that there is no reality. It means that quantum mechanics does not pretend to be any kind of theory which describes the sub-microscopic world. It is a (possibly complete and presently the best) theory of how our interactions with the sub-microscopic world will work out.

Skippy

GeorgCantor

Philosophically, what does it mean for a quantum system to have NO objective existence prior to observation/measurement, as that was Bohr's insistence? Bohr claimed that 'particles' do not possess properties when they are not being observed.

What is the ontology that is consistent with this premise, but solipsism?

GeorgCantor

This is wrong. Bohr led a 30-year debate(possibly the longest in science) that QM was a complete theory. The completeness of QM was the central point of the debate between Einsten and Bohr.

JoeDawg

Ontological solipsism denies the existense of 'other minds', but affirms the existense of the conscious self.

Observation/measurement, in terms of QM, doesn't even require one mind.
In QM, observation, is all about 'interaction'.

Consider what happens when you crumble a piece of paper, it begins interacting with itself, in a way it does not when it is flattened out. Solipsism gives primacy to one really crinkly bit of the paper and defines the rest of the piece from that perspective. QM doesn't, all crinkles are treated equally.

But flatten it out again, and the crinkles disappear. The paper is not reality, because there is no way to describe a lack of interaction. Physics only appears with the friction of paper against paper, the crinkles.

GeorgCantor

This is a bold statement. The problem is that it is based on an assumption that there exists a mind-independent reality that does not require a mind. I am perfectly aware that Bohr never made such a statement and we are discussing Bohr's ontological propositions for reality.




Bohr explicitly said that unmeasured phenomena are not real. What he made of that ontologically is not clear to me, but it looks like solipsism. I am not even sure an ontology is even possible on the proposition that unmeasured events are not real.






We are not talking of QM in general, where there is still NO agreement on what the theory means, though you very strongly imply and believe it is otherwise. We are talking of the QM of Niels Bohr. Niels Bohr assessment was that "unmeasured/unobserved entities are not real". Bohr insisted that his QM was complete which means that that is how reality is.


I contend that "unmeasured/unobserved entities are not real" is a form of solipsism. I see no reason to believe that someone who denies the objective reality of objects with fixed properties in time and space will believe in the existence of other minds. What would drive such a belief?


This discussion requires that i remind of his famous quote:

“If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet.”



Or let's re-run the argument as it was in 1935:

Einstein: - Do you really believe the Moon is not there when nobody is looking?
Bohr: -Yes, it's not there when nobody is looking.


What is this if not a form of solipsism?

JoeDawg

Not really, if reality is defined as (observed) interaction.
Correct. I don't see a problem, unless you limit the idea of 'measurement' to 'measured by a conscious' entity, as opposed to 'measured' being equivalent to 'interaction'.

When two atoms bounce off each other, energy is converted.... that would be a form of measurement... a very basic observation. Just like the detectors used in the LHC, for instance.
Sure.
I never said I agreed with any of this. The question was:
Answer: Reality is interaction. Whether Bohr would agree with me, I don't know. Never met the man, but I see no reason to believe Bohr was ontologically solipsist. I think you're getting hung up on the word 'reality'.
Still not seeing where solipsism comes in. I don't think he was implying that if Niels Bohr didn't observe something, then it doesn't exist. Is this what you mean? That would be solipsism. But QM doesn't require an conscious human 'observer'. I'm thinking Bohr knew that. Do you have a quote that contradicts this?
I contend you are wrong.
I don't think he was doing that. After all if you observe an object existing in time and space.... then according to Bohr, it is real.
Interaction with other minds?

GeorgCantor

And how does the above statement lead to the conclusion:


except by assuming that reality exists even without a mind?




Bohr's position was that unmeasured entities were not real. My position DOES NOT matter at all as that is not the subject of the thread.






But you did state:


This is your belief and you made it into a strong statement.





We do not know what reality is, or even how it is. The formalism of QM does not address these issues. They are philosophical and when Bohr was being philosophical he stated:

""Everything we call real is made of things that cannot be regarded as real."


He also states that wavefuncions are not real and unobserved entities, e.g. the Moon when nobody is looking does not exist.




Go teach Einstein and tell he didn't understand Bohr's points correctly. You need to reread the EPR.




Who said anything about the current trends in QM? We are at QM as it was "understood" around 1935.




Yes, according to Bohr, quantum systems do not have definite properties prior to observation/measurement. And this is very widely known as the CI of Niels Bohr(that Einstein argued against). Or are you saying it is possible to exist and be real without having definite properties? That would be absurd.





How did you prove that unreal(according to Bohr's view) superposition of states actually exist(according to Bohr's view)? You did not.




So reality is real because it is real? Ha, great way of arguing but that was not Bohr's point at all.











Let's re-run the argument as it was in 1935:

Einstein: - Do you really believe the Moon is not there when nobody is looking?
Bohr: -Yes, it's not there when nobody is looking.

What is this if not a form of solipsism?





If Bohr is right, i'd be cautious with that belief.


The EPR argument between Bohr and Einstein was because of Einstein's concerns for Realism after the arrival of the Copenhagen Interpretation of Niels Bohr. Einstein believed as you do, that objects have properties whether anyone chooses to measure them or not at all times. Niels Bohr was of the opposite opinion and this is closer to solipsism than any other ontology i can think of.

JDStupi

Maybe I am missing something, and it is possible that I am, but why haven't we considered Bohr's position as idealist? I believe it is consistent with all of the statements attributed to him (the ones in this thread at least, I am by no means familiar with his statements regarding reality as described by quantum theory), and for me, solipsism is too large a jump to ascribe to Bohr

glengarry

My 2 cents... the entire point of "complementarity" is to make room for the possibility of a classical spacetime theory that is capable of accounting for the essence of Nature, as she is immediately experienced (i.e. "measured"). So, Bohr's stance, in my view, was much more philosophically sympathetic towards the two competing tendencies of mankind to 1) be certain of some fact and to 2) understand how that fact is at all possible.

But the new generation of theorists (e.g. Heisenberg, Pauli, etc.) saw fit to stop trying to understand empirical reality, in its possibility--and simply held fast to varying forms of ontological skepticism or outright denial (not atheism, but aontism?). And it was for this reason that Einstein dedicated his entire post-relativity career to keeping alive the hope that a "complete" theory of physical reality could indeed, in time, be found.

GeorgCantor

It could be of course. The question is how does one remain idealist for long? If someone believed that all of reality is just in the mind, wouldn't that lead him/her to doubt the existence of other minds? What justification would an idealist have for the belief of the existence of other minds(provided they didn't believe in the realness of experienced reality)?

JDStupi

True, that is a valid question that possibly the more philosophically informed could reply to. I would guess that it is all about not proceeding beyond from what is directly "empicrically" available to us through our senses, and the conception that there exists an external material reality does not follow from what we experience as "sense-data". Yet our interacting with other minds makes the existence of other minds seem more plausible. But at that point I suppose it would be right to say that denying external reality due to it not following could also be said of other minds, though that is more radical. I would be interested to see how an idealist would discuss that issue.