This is what I would like to see discussed. Does the moon truly not exist if we do not observe it? What constitutes as evidence of existence and truth? — MTravers

We were just discussing similar questions in another thread. My position - if the answer to a question is can not be determined, even in theory, it doesn't have a yes or no answer. It is a metaphysical question, a matter of preference and usefulness. It is very useful for us to assume that the world exists even when no one is watching.

Thank you for your reply. Okay, if the answer might be the truth about the existence of something cannot be determined as having a yes or no answer then that belief / assumption must be thoroughly examined to see if it is true. So the question is now why can't we prove or disprove the existence of the moon? In this case Bohr says that the existence of the moon cannot be determined. On what logic and, or evidence is he basing that assumption? I think that it is fairly easy to prove that the moon exists without directly observing it.

My concern now is if Bohr is correct all of science and the scientific method is called into question. If a single observation in time by multiple observers is not considered as evidence of existence then we have a problem. The problem happens whenever we don't do the experiment. If we choose to not continually observe the results of an experiment the second we stop the experiment, the experimental result becomes instantaneously meaningless. Whatever it is we were measuring returns to an unknown state as soon as we stop observing it. If we truly believe that is true the study of the Universe becomes pointless. I do agree with what you say as it is very useful and sensible that the world exists when we are not watching.

What is the Topic of this other discussion? I would love to observe that discussion

I think that it is fairly easy to prove that the moon exists without directly observing it. — MTravers

I interpret Bohr's comment not to refer to just seeing or other direct observation, but also indirect observation e.g. measuring the effect of the moons gravity on the oceans. If my understanding is not correct, then the question becomes trivial.

So the question is now why can't we prove or disprove the existence of the moon? — MTravers

Let's try this:

• Assumption - we cannot perceive the moon directly or indirectly.
• Definition of "prove" - Demonstrate the truth or existence of (something) by evidence or argument.
• Proposition - The existence of physical phenomena can not be proven without physical evidence, i.e. argument in the absence of evidence is not good enough.
• Definition of "evidence" - Facts or information indicating whether a belief or proposition is true or valid.
• Proposition - Physical facts and information are only obtainable by direct or indirect perception.

Einstein should have asked Bohr how he can prove atoms exist because no one had ever seen an atom. We infer their existence by the effects they have on the things we do see.

We can prove the moon's existence without looking at it by pointing to the tides. What causes the tides on Earth, if not the moon?

The strongest argument against this kind of claim, in my view, is what happens when you consider events which predate the advent of consciousness. This does two things:

(1) It reveals that there is a time in which all that is was unconditioned by the ideational imposition of 'form', or similar concepts; anything which produces a relativisation of space and time as such to perceptual space and time.
(2) It reveals that whatever our consciousness does, it dwells within this apparently unstructured universe radically indifferent to but nevertheless consistent with the advent of our consciousness.

More precisely, considering the universe prior to the advent of consciousness reveals a becoming which is not reducible to a becoming for a human. In the language of Locke, this is an affirmation of the difference between primary and secondary qualities - primary qualities are those which are not determined by their relationship to a person; like curvature, specific heat capacity, temperature, chronological age...

Levi Bryant articulates it (following Meillassoux) here:

By contrast, when we speak of primary qualities were are speaking of non-relational properties that are in the thing itself. These properties are non-relational in the sense that they do not depend on us in order to exist. As such, they are characterized as the “in-itself”. For Descartes these properties consisted of length, width, movement, depth, figure, and size. Meillassoux, by contrast, adopts the thesis that any aspects of an object that can be formulated in mathematical terms belong to the object in-itself.

this is not necessarily to affirm that properties such as temperature, distance, curvature are non-relational tout court, but they have their own specific strata of relations which cannot be seen as reducible to a relationship between them and a person. Such as temperature being a result of relations of motion of particles, curvature being generated from constitutive spatial (more generally, parametric) arrangements of an object.

I am okay with the following statements you make.

Definition of "prove" - Demonstrate the truth or existence of (something) by evidence or argument.
Proposition - The existence of physical phenomena can not be proven without physical evidence, i.e. argument in the absence of evidence is not good enough.
Definition of "evidence" - Facts or information indicating whether a belief or proposition is true or valid.
Proposition - Physical facts and information are only obtainable by direct or indirect perception. — T Clark

I don't I agree with the "Assumption- we cannot perceive the moon directly or indirectly" Maybe I am not understanding you. Please give an example. I am of the opinion that an individual can perceive the moon directly and indirectly.

I am also not sure if Bohr meant indirect observation as well. If I were forced to guess I would bet he was thinking in terms of Schrodinger's Cat as in making a direct observation as to whether the cat is alive or dead which cannot be done unless you make a direct observation That is why I used the word "directly".

Proof for the existence of the moon.
1. The moon's tides are an excellent indirect measurement that can be reliably made to confirm the existence of the moon. That was the first thing that came to mind.
2. I can use astronomical charts and computations to predict where in the sky the moon will be. I can then go outside and look up at the sky and confirm that the location of the moon matches the charts and computations. We can use mathematical models to predict the position of the moon.
3. We physically had astronauts land on the moon and take pictures of the earth from the moon. The astronauts photographed the moon as well. Millions of people all agree that evidence is real and valid.
4. The astronauts also brought back hard physical evidence in the form of moon rocks.

I see a lot of hard evidence that proves the existence of the moon. I believe that we recognize and perceive evidence of reality via our consciousness. So reality is not not defined by our consciousness it is only recognized using the tools of our senses and the mind. I cannot think of any evidence that supports Bohr's idea that the moon cannot be proved or disproved.

I don't I agree with the "Assumption- we cannot perceive the moon directly or indirectly" Maybe I am not understanding you. Please give an example. I am of the opinion that an individual can perceive the moon directly and indirectly. — MTravers

This is just my interpretation of what Bohr was saying. I was using it as the basic assumption so I could try to trace its consequences.

I am also not sure if Bohr meant indirect observation as well. If I were forced to guess I would bet he was thinking in terms of Schrodinger's Cat as in making a direct observation as to whether the cat is alive or dead which cannot be done unless you make a direct observation That is why I used the word "directly". — MTravers

As I said in my post, I interpret Bohr's statement to mean direct and indirect perception. If that isn't what he meant, the whole question dissolves and I agree with your position.

The only fact that we have is that experience exists. The proof for existence of other things outside and inside is difficult if not impossible.

Albert Einstein is reported to have asked his fellow physicist and friend Niels Bohr, one of the founding fathers of quantum mechanics, whether he realistically believed that 'the moon does not exist if nobody is looking at it.' To this Bohr replied that however hard he (Einstein) may try, he would not be able to prove that it does, thus giving the entire riddle the status of a kind of an infallible conjecture—one that cannot be either proved or disproved.

This is what I would like to see discussed. Does the moon truly not exist if we do not observe it? What constitutes as evidence of existence and truth? — MTravers

Is it an infallible conjecture? I agree there's a sense in which the relevant sort of conjecture is unverifiable and unfalsifiable. But to say a claim is unverifiable and unfalsifiable is not to say it's infallible.

I see no reason to suppose that a thing like the moon does not exist while we do not observe it. On the other hand, arguably there is at least one reason to suppose that a thing like the moon does exist while we do not observe it: because that supposition leads the way to the simplest account. For if there are lapses in its existence when it's not observed, we should want some account of how this happens to be the case, and it seems most reasonable to expect no definitive answer is forthcoming; whereas the contrary case leaves no such gap. By the simplest account, things in general are said to proceed the same way whether they are observed or not, excepting special cases.

Perhaps that has a metaphysical ring to it. We can address the question another way: Even if I'm not currently observing the moon, I have a pretty good idea where to find it, and what steps I might take to observe it from my current position. Any object that remains available to us in this way is said to "exist" even when it is unobserved. This is not a metaphysical thesis, but only a rule of use for the word "exist". Along these lines, we may remain agnostic on the metaphysical question, or even deny that it makes sense to ask such questions, while saying that the object continues to exist, to participate in the world, even while it is unobserved.

I had read that it wasn’t Neils Bohr that Einstein asked, but his friend Michael Besso on an afternoon stroll in the forests. It was asked with a tone of exasperation - like ‘surely you can’t believe that the moon doesn’t exist when nobody is looking at it!?!’ It is indeed true that Einstein and Bohr then went on to discuss such questions for decades afterwards, but the original question was asked of Besso (according to Walter Isaacson's biography of Einstein.)

The real question is: what obliged Einstein (of all people) to ask that question, at that point in history?
Einstein, as is well-known, was a physicist, not a philosopher, albeit a scientist with philosophical interests. But the point is, the question arose directly as a consequence of the work then being done on the nature of matter by Einstein, Bohr, Heisenberg, Pauli, and others (all of whom were brilliant scientists of the highest order.) Heisenberg, who was a younger contemporary of them (he made his major breakthroughs at an exceptionally young age) recounts that on various occasions he was brought to tears by the ferocity of the debate between the participants on the implications of quantum theory. Bohr, for his part, said 'that if you're not shocked by quantum physics, then you haven't understood it'.

And the reason for that, and for Einstein's question, was precisely because the discoveries of physics cast doubt on the notion that the objects of scientific analysis really existed independently of the act of observation. This is what is shocking, and what lead to Einstein's question. And the question still remains.

A realist would naturally assume that 'the atom', or whatever the fundamental unit of matter turned out to be, would exist regardless of it being observed or measured. But the implications of the uncertainty principle and 'the observer problem' were that in some sense, sub-atomic particles didn't really exist as a discrete unit, except for when they had been measured. For some reason, the very act of measurement had a causal effect on their ontological status. This is the well-known 'collapse of the wave function' effect which has been subject of dispute and conjecture ever since.

Some relevant essays, articles and books:

Quantum Mysticism: Gone but not Forgotten Juan Miguel Marin

Quantum weirdness: What we call 'reality' is just a state of mind Bernard D'Espagnat

The Mental Universe Richard Conn Henry

Quantum, Manji Kumar

And the debate is on-going.

One problem with citing Quantum Physics as a basis for philosophical speculation is that physicists are usually mediocre philosophers and philosophers are usually mediocre physicists.

Another problem is the often unacknowledged assumption that the microphysical is the only "fundamental" reality.

Well if one agrees with Einstein that objective reality is the way the Universe works and he is correct in his mind experiment concerning the moon. I think that many people if not most people would agree that in fact the moon does exist when it is not observed. So far we have only seen evidence that it exists whether we observe it or not.
The only way to prove that the moon really has the capability of suddenly not being there and drops out of existence when we stop looking at it is to see a sudden disappearance of its gravitational effect. That has never happened. The moon's gravity has always been there and has never vanished therefore the moon has always been there since its creation. The possibility that the moon would not be there simply based on its not being observed is not even a possible outcome.
If that turns out to be correct then Quantum Mechanics has a problem with its interpretation of how physical reality works. The moon even though it is a macroscopic object, is itself composed entirely of sub-atomic and atomic microscopic objects. Therefore if the moon is an element that exists independent of our observation then all the atomic objects inherit from this fact that they now have observable paths and velocities as a whole because the moon has an observable velocity and path. All of those un-observable microscopic objects are now elements of physical reality. That might be a bit of a stretch but I can't seem to find away to defeat Einstein's simple argument. It seems now that in reality even though the mathematics of QM works very well it can't really be relied upon to explain why or how things happen. This is becoming quite a conundrum.

I read somewhere - I forget where - that a research project had been commenced in the Stanford Physics Labs to try to answer this question once and for all. I can't remember the details, but I think it involved something to do with quantums and some very expensive measuring apparatus.

Until results are obtained from that or a similar project (there was mention of developing a network of international labs to work on it and share results, possibly involving the accelerator at CERN), we can only speculate.

I read somewhere - I forget where - that a research project had been commenced in the Stanford Physics Labs to try to answer this question once and for all. I can't remember the details, but I think it involved something to do with quantums and some very expensive measuring apparatus.

Until results are obtained from that or a similar project (there was mention of developing a network of international labs to work on it and share results, possibly involving the accelerator at CERN), we can only speculate. — andrewk

I believe there is a 74.95 possibility you are not serious. It would be higher except that philosophers are willing to consider almost any silly idea.

Anyone care to venture why Neils Bohr said ‘if you’re not shocked by quantum physics then you haven’t understood it?’?

(Note the two question marks. That is because it’s a question about a question, although that’s not important.)

We've already been doing this topic to death in another thread, but as a fresh encapsulation, I'd say: the most you can say is that the way the moon exists for you when you're looking at it doesn't exist when you're not looking at it, but the ways the moon exists for other things (its interaction with other parts of the world that are not-you) still carry on when you're not looking at it.

This is harping on my main theme of Externalism as being the proper solution to most of these sorts of problems related to consciousness. Consciousness is not the name of a process that goes on just in the head, in the skull, in the brain; it's the name of a process of interaction that actually bridges and connects things (actually physically, literally) and includes both of the interacting processes within itself.

It's a bit analogous to the roles we play in society - for my co-workers, I'm their boss, for my family I'm the father, for my wife her husband, for my friends a best mate, for my amateur sports team at the weekend, I'm a certain position in the team. In each of these presentations of myself to the world, the other aspects of my potential self-presentation are absent because they're not being presented to their respective receivers. (When I'm with my family, I'm not a teammate, etc.)

Similarly, being in general isn't a monovalent property, but a multivalent property. The aspect a thing has for me, it has only because the interposition of my brain and sensory apparatus at that time and place, affords an opportunity for the thing to manifest a "side" of itself that it could never have manifested without that opportunity - and likewise, it presents me with an opportunity to manifest a new, hitherto-dormant (or hitherto-merely-possible) side of myself to it.

Again, going back to the interpersonal level, that's one reason why we value relationships - because being with different people draws different aspects of ourselves out of us, it actually gives us more opportunities to manifest aspects of our own existence. (And often that reflects back into self-consciousness - for example, it's common for a musician to play their track to a friend, and hear it in a different way "through his ears," so to speak.)

:up:

Actually, your quote is generally attributed to The Philosophical Writings of Niels Bohr, David Mermin, notes that when reviewing the three volumes of The Philosophical Writings of Niels Bohr, he couldn't find any mention of it.

Other things Niels Bohr is reputed to have said;

It is wrong to think that the task of physics is to find out how Nature is. Physics concerns what we say about Nature.

Isolated material particles are abstractions, their properties being definable and observable only through their interaction with other systems.

So, in answer to your question, he probably didn't say anything of the sort, and if he did, it's unlikely that he meant that any brand of mystical woo is now on an equal footing to science.

That Einstein quip about the Moon should not be taken too literally (or at all literally). Its context is a scientific debate about quantum physics, which is wide-ranging and in large part philosophical in its own right, but since this is a metaphysics & epitemology section and your line of questioning doesn't seem to engage with that specific debate, we can leave it aside. Suffice it to say that in the context of the historical debate, indirect observation most definitely counts as an observation. If you can observe indirect effects of the Moon, that means that its wavefunction has long since "collapsed" (to use Bohr's preferred interpretation), so the question is moot.

Does the moon truly not exist if we do not observe it? What constitutes as evidence of existence and truth? — MTravers

That suggests that the moon does exist, if we are observing it.

But the way in which things exist when we are observing them involves us, the nature of our senses. For example, that I see the moon as a certain colour is a function of my eyes and my brain, not the moon in itself.

So, if I am not looking at the moon, it certainly does not exist, not in the same way it does when I am looking at it.

Similarly, being in general isn't a monovalent property, but a multivalent property. The aspect a thing has for me, it has only because the interposition of my brain and sensory apparatus at that time and place, affords an opportunity for the thing to manifest a "side" of itself that it could never have manifested without that opportunity - and likewise, it presents me with an opportunity to manifest a new, hitherto-dormant (or hitherto-merely-possible) side of myself to it. — gurugeorge

Perhaps the Moon is the manifestation rather than the external thing(s). I'm not particularly keen on reductionism, which I think is unavoidable otherwise. When I talk about the Moon (or apples, or cats), am I really just talking about a particular mass of particles? There's more to it than that.

When I talk about the Moon (or apples, or cats), am I really just talking about a particular mass of particles? There's more to it than that. — Michael

Surely what you refer to when you are talking about the moon changes depending on the context. If you were recounting a horror story about werewolves, then 'the moon' would refer to a frightening portent of danger, but when at your job at NASA, piloting the Apollo capsule, you are referring to the mass of particles (or more correctly the model of the physical world we currently share) because its the gravity from those particles that's going to guide the capsule.

I think this is the source of a lot of philosophical smoke and mirrors. Taking the ambiguities of one context and applying them to another.

Perhaps the Moon is the manifestation rather than the external thing(s) — Michael

Well the moon we experience is the only manifestation of anything we know, and it's external in the relevant sense of existing (in its other "faces" for other things) regardless of whether we're experiencing it or not.

I don't think there's any philosophical need for a split between manifestation and something hidden behind it. Philosophically speaking, we can coherently say that we experience what there is, because what we experience is the only place where our sense of "is" comes from, it's the meat and potatoes of existence so far as we're concerned.

Whether we get some revelation or news from afar of something other than what we experience, as we experience it, being all there is, and whether we believe that or not, is another story, but I don't think it's necessitated by any philosophical reflection, for example as a posit to make sense of what we experience.

and it's external in the relevant sense of existing (in its other "faces" for other things) regardless of whether we're experiencing it or not. — gurugeorge

That's the thing I'm questioning. If the Moon is the manifestation then it doesn't exist when we're not experiencing it, just as the character in a game I'm playing doesn't exist when it isn't being rendered. Of course, there's still something that continues to exist when not being experienced (or rendered), but that thing isn't the Moon (or the character).

So rather than say that the Moon exists which then appears to us a certain way, it's rather that some unspecified thing(s) exist(s) which then appears to us as the Moon. In terms of physics, there's no distinction between these two interpretations, but there is a conceptual difference, and I think my approach helps avoid naïve realism and, as I mentioned before, reductionism.

I don't see why you can't just say it's the moon that exists.

The manifestation (the "face" it shows us) doesn't exist outside that interaction, but that doesn't mean you can't say that the manifestation is the moon - it is after all a manifestation of the moon, not some alien thing that's not-the-moon.

Going down this route would probably get us into mereology - re. what kinds of part/whole distinction are legitimate in this context. A leaf isn't a tree, but a leaf is tree, it's part of the tree-iness of the tree.

For example, suppose you see a leaf filling the screen in a movie, then the camera pans out, the leaf is part of a bunch, which are then revealed to be part of a tree. When one was looking at the leaf initially, was one looking at the tree? In one sense no, one was just looking at a leaf, but in another sense yes, one was looking at the tree, at one of its leaves.

I think we can treat objects in general in a similar way: the particular form of existence a thing has in interaction with us, you can say it's a distinct thing (like the leaf), but you can also say it's a manifestation of the thing (its being part of the whole tree, or in this case one of the object's possible ways of being, sc. its way of being for us).

I am also not sure if Bohr meant indirect observation as well. If I were forced to guess I would bet he was thinking in terms of Schrodinger's Cat as in making a direct observation as to whether the cat is alive or dead which cannot be done unless you make a direct observation That is why I used the word "directly". — MTravers

Why would it be an either/or with the cat being either dead or alive? Why would the "cat" not exist in an infinite number of states until we look at it? Why could it not change into a dog inside the box when we look at it?

There must be some universal determining factor that precedes our observations.

There are any number of related inquiries.

How might I prove to you that I'm self-aware?
Does it all cease to exist while I'm unconscious? Only to re-emerge when I come back to?
A blind person does not see the Moon; a synesthete might smell it.
A dead (or hypothetical) person cannot prove (or know) anything, let alone about the Moon.
If all else is (existentially) dependent on my experience thereof, then it all seem to part ways with ex nihilo nihil fit for example.
Can an unseen boulder falling off a cliff kill you?
Is phantom pain evidence of a real limb, or more, say, like a hallucination?
What's the deal with alien hand syndrome?

To me at least, it makes (significantly) more sense that I'm but part of a (significantly) larger world.

A lot of good concepts here. I would like to think about everything that was said and perhaps make an attempt at a solution to the dilemma. The solution will have to have in its explanation the mechanics of how the mind and consciousness function in the physical realm. In order to do this the origin of human consciousness will have to be included. This will require some discussion of spiritual components. Hopefully this is okay. Its a philosophical opinion. Testimonial evidence will be given to a limited extent. The goal is to get to the truth. I assume that for any problem there is always some answer. So the answer to whether the moon exists as independent object from our observation should have a definite answer. Either it does exist independent of our conscious observation or does not exist or some how both cases are true in some sort of duality solution.

What the Realist (Realist about a World independent of Mind) believes is that the existence of the moon is independent of the mind or of consciousness: if you took away all consciousness of the moon whatsoever, all perceiving of it, feeling it, seeing its effects, feeling its effects, thinking of it, dreaming of it, remembering it, believing in its existence—there’d still be a moon. This means he believes the following postulates:

• There is something other than Consciousness or Mind; Consciousness is one of (at least) two things; Consciousness is finite; there are (at least) two things.
• There is such a thing as the Unknown; there are two types of thing: the Known and the Unknown, Consciousness is not the only type of thing.
• Consciousness is not Reality itself; Consciousness is part of Reality; Consciousness is mere Appearance.
• There is a greater reality than Consciousness; there is something that is both Consciousness and the Unknown; there is an Objective.
• There is such a thing as a Whole is made up of Parts. (There is Consciousness and the Unknown and the whole of Reality).

(He need not however believe these postulates are exhaustive, or that this individuation of them is definitive.)

—And from these basic postulates, the Realist constructs his world.

There are many ways in which these postulates may be realised or visualised. The big ones, the original ones, are Space and Time. According to the spatial realisation, Consciousness is conceived as in certain places (where brains are)—and it is also conceived that there are other places, where they are not. According to the temporal realisation, Consciousness is conceived as when sentient beings are—and it is also conceived that there are other times, when they are not (earlier than them and later than them).

Realism is the basis for Science: Unknown and Known become, respectively, Physical World and Scientist.

(There are also deeper sceptical questions: Is there anything at all other than this experience, my experience? That is, not just, “Is there anything physical outside Consciousness?” but “Are there even two things? Is there even another consciousness?” And one deeper still: “Is there anything other than this experience I am having now?” —But these are outside the scope of this thread.)

I think the realist you are talking about has at a bare minimum just four metaphysical commitments:
1) that there are things that perceive
2) that there are things that are perceived
3) that there are perceptual relations between these things, i.e. relations we indicate with verbs like "to see", "to hear", "to touch" and so on.
4) neither of the types of things (1) or (2) depend for their existence on the fact that those relations sometime hold between them.

Empirical idealists, like Berkeley and perhaps Bohr - although I cannot be sure about him - deny (4) and claim instead that things that are perceived depend for their existence on being perceived. You can find his arguments for that conclusion in the first Dialogue Between Hylas and Philonous.

Where does this leave the moon when everyone's gone to sleep? Berkeley's answer was that God never sleeps, and perceives all things at all times.