Carlo Rovelli posits that the observer will cause the system to collapse so that a measurement can occur but he thinks that this collapse is only localised to the interacting systems and nowhere else.
The system does not collapse from the standpoint of non-observers.
At least, I think that's his posit. I heard it in a podcast between him and Shaun Carroll

The measurement problem in physics relates to Heisenberg and Schrodinger... — Edmund

Are you referring to quantum measurements of vectors when the wave function is operational?

...but in essence revolves around the possible "influence" of the observer/measurer. — Edmund

Are you asserting the presence of the observer as the main cause of Heisenberg Uncertainty? If so, I suspect this is a major proposition you should propound.

Berkeley's view that to be was to be perceived seems therefore particularly precient? — Edmund

I suppose we know that observer-observed are contemporaneous. What do you have to say about unobserved things? Do they exist?

The measurement problem in physics relates to Heisenberg and Schrodinger but in essence revolves around the possible "influence" of the observer/measurer. Berkeley's view that to be was to be perceived seems therefore particularly precient? — Edmund

Heisenberg's original paper on uncertainty was based on the observer effect - any light I aimed at a particle to measure either it's position or speed would add energy to the system and make measurements of the other property less accurate. That makes sense to me, but it is my understanding that this explanation is now considered incorrect. Here's what Wikipedia says:

Historically, the uncertainty principle has been confused with a related effect in physics, called the observer effect, which notes that measurements of certain systems cannot be made without affecting the system, that is, without changing something in a system. Heisenberg utilized such an observer effect at the quantum level (see below) as a physical "explanation" of quantum uncertainty. It has since become clearer, however, that the uncertainty principle is inherent in the properties of all wave-like systems,

It seems to me that this means that what Berkeley was talking about is something different than the uncertainty associated with quantum mechanics.

This is essentially true from a number of perspectives outside QM. Whether or not it is true for QM depends on your definition of "perceived," and the interpretation of QM used, specifically the ontological status of wave functions. I do not believe your quote would apply under most interpretations because wave functions are understood as existing. Second, the phenomenon you would be referring to would be wave function "collapse" or decoherence, not the measurement effect.

"Observed" and "perceived" are loaded terms, and it is somewhat unfortunate the CI version of QM uses the word observer in English, because it causes a lot of confusion. In normal language, a rock does not perceive things, nor does a photoelectric sensor. In CI QM though, a photoelectric sensor can absolutely be an observer. Macroscopic objects like rocks can absolutely cause decoherence.

Decoherence as a concept has its own problems and critics, but I think the gist is easier to get than the CI language. When a quantum system, a light wave for example, interacts with its environment, phase information about it gets scrambled with the environment. We say it loses "phase coherence," because it can no longer be represented as the original wave function. So, if you think about the double slit experiment, and how the light waves interfere with each other, decoherence is the opposite of this phenomena. You can think of quantum elements that decohere as becoming entangled with the environment.

So, "being observed" can be a bit misleading because of the way the word is normally used. Other explanations will describe the shift occurring when "information is acquired about the system," or describe it as a sort of friction between the system where it is essentially shedding information instead of heat (I don't like the friction analogy much because it can twist concepts if you're already used to thinking of energy as information, and it uses a classical image of space, with objects with identities rubbing against each other that is not the best for understanding QM).


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However, the statement is true from a methodological perspective. If something truly cannot be observed, either directly or indirectly through its relationship with observable entities, not by us humans, and not by any sort of hyper-advanced species, then it cannot be said to exist using empirical criteria. For it to be said of a thing that it is true that it exists under such criteria, it must be observable.

We could push this further. We could imagine that there are other universes, with different laws of physics, and different entities, sitting outside our own. We can never interact with them. However, we would still say that, if such a universe existed, then those things would have being, even if from a purely empirical perspective, their being and not being are co-identical.

But what about a hypothetical particle the "nullon?" The nullon would be a fundemental particle or field, but unlike the other fundamental particles, it interacts with nothing. Nullons permeate the universe, but nullons do not have any relationships with anything else in the universe. Additionally, nullons do not interact with each other. If we envision them as particles, we can imagine them just passing through each other without a trace; they cannot be observed, even by other nullons.

Can the nullon have being? I would argue it cannot. It's being and not being are forever and always, for all things, co-identical. If it shares an identity with its not being, even if it is, it cannot be.

Ironically, under Leibnitz Law, it appears it could have identity. If "x is identical with y then everything true of x is true of y" would hold for the nullon, although it would also share an identity with all non-existent things. I'm aware of ontologies that hold that just such a category is definitionally a part of being, and essential for it as creating a definition for being. In those cases, the reverse of your quote is true "there must be things that cannot be observed for things to be."

The nullon sounds a bit silly, but this is essentially the thing substratum metaphysics argues exists, i.e., that there are entities of pure haecceity. It's understandable that people do this though, because if you instead posit that things are merely the universals they exemplify of a collection of tropes, you end up with some other weird, circular issues.

There is another sense that the statement is true in too. In order for anything to be for anything else, it must interact with it. Its being and non-being cannot be co-identical for it. However, in the framework of physics, you can't meaningfully talk about taking up an observation point that isn't physical. Your observation point must be a physical system, it cannot be magic. This has the effect of also making it a necessity that X has to interact with Y for it to be "for Y." Talking about some sort of "absolute being" in physics doesn't make sense, except as a useful simplification for understanding concepts.