If existence means interaction, how could there ever be a wave function of an existing particle? I have no formal education in physics so what follows could contain a lot of wrong assumptions. If that is the case, feel free to close this. If you do find something worth answering please know that math will not help me understand because I'm not a physicist, but do include it if it is the only option.
According to the Coppenhagen Interpretation particles do not have  a specific location in space and they "move around" randomly, unless they are "observed".
Is Observation the same as Interaction ?
By "observed" I understand "unless something interacts with that particle". I say that because it is a never a human interacting with the quantum particle: it's always a bunch of other particles interacting with that quantum particle. The human is simply the one that reads the data afterwards. For example, in the double-slit experiment, that "something" could be a photon detector interacting with the quantum photon. And by "interacting" I mean it's the particles of the photon detector (however the device works/whatever those particles may be) that are interacting with the quantum photon.
And in that case, because there is interaction, the "wave function" collapses and the particle gets a location. More specifically, the wave function collapsed because the particles of the photon detector interacted with the photon being tested. It collapsed because of that interaction between particles, and only that and nothing more. Is this assumption correct ? Does the "wave function" of a particle X collapse only when that particle X interacts with at least one other particle?
How could there be a wave function if particles always interact ?
If it is not possible for a particle to not interact with something else how could the physical world be intrinsically and literally probabilistic, given that there is no room and no time for a probabilistic state if interactions are constant and therefore the "wave function" not only constantly collapses but actually there's never any room for it to exist in the first place?
How can a particle, that doesn't interact, exist ?
If it is possible for a particle to not interact with anything else (and therefore find itself in this state of "superposition") how can this particle exist in the first place ? Doesn't physics always define the nature of a particle through its interactions with the rest of the particles ? Can the existence of a particle be defined indendent of its interactions with other particles? So using the CI terminology,  if a particle is not interacting with anything and therefore has no reason to be at point A in space instead of point B, why did physicists then choose to say that that quantum particle is "everywhere" instead of simply saying that it is "nowehere" and therefore literally doesn't exist?
In other words, when we shoot a quantum photon from a canon during the double-slit experiment, wouldn't it be more accurate to say that we're actually not shooting a photon from a cannon but instead, we're shooting a set of conditions for a photon to exist in the future, if those conditions happen to interact with the rest of the world in a certain way ?
Why do we talk about existing particles of unknown location instead of conditions for not-yet existing particles?
Doesn't a big part of the "weirdness" in QM arise from the fact that physicists, even though they can't locate the photon, they nonetheless choose to acknowledge its existence even before they acknowledge its location, while it is in that state of unknown location ?
Afterall, a physicist will say: "we don't know where the photon is located unless we observe it"  but they're nonetheless already talking about a photon and not a proton or a pineapple, therefore acknowledging its existence even before they locate it. And if so, why do physicists do that ?
What is wrong with just saying: Particles in the quantum world don't always exist, what always exists is a set of conditions, that could or could not give rise to a particle if they interact with the rest of the world in a certain way? Obviously, the work is not done, now we have a new problem, to investigate those "conditions", but nonetheless, in this case, there is nothing "weird" about the quantum world:
I can perfectly accept the idea of a distinct set A of conditions inside a box, that when they interact in a certain way with the outside world we will call this set of interactions X an "electron" (but never a proton or something else) and another distinct set B of conditions inside a box, that when they interact in a certain way with the outside world we will call this set of interactions Y a "photon" (but never an electron etc.) and so on. When these conditions are not interacting, they simply don't "give rise" to a "photon". There is no magic there. It's actually perfectly "classical" if we dare to think of an analogy in the macroscopic world where we can call a set of conditions X "a piece of paper", and if those conditions interact with high temperatures, they can give rise to fire, but if they don't interact, they will not.
To clarify, I'm not talking about a "hidden variables theory" where the photon exists but we can't locate it because we're not aware of these "hidden variables". I'm saying that the photon doesn't exist to begin with, but only a set of conditions that could allow it to exist if those conditions interacted with the rest of the universe in a certain way, and it is those conditions that are right now (at least) "hidden". And is this the quantum field theory I'm describing ? In which case I can't find anything weird or non-classical about it: I don't know what these "conditions"  are, I don't know how they do what they do, but at least the idea of conditions C giving rise to particle P only if they interact with the world in a certain "way" W is not non-sensical to me.
 A: I suspect you question will be closed, as it is really about the meaning words and not properly about physics. However, I will have a stab at trying to resolve some of your conceptual issues.
Firstly, 'observations' of particles does mean interactions between the particles we are observing and other particles which form the detecting apparatus. If there was a type of particle that never interacted with other particles in a way we can an observe then we would never know about it, and we might conclude that such particles didn't 'exist' because we had no means of ever being able to show that they did.
However, your suggestion that we might only consider a particle to 'exist' when it interacts with other particles- which implies that it does not 'exist' before the interaction- is untenable for a number of reasons. The most obvious is that we have various conservation laws which would be breached if particles stopped 'existing' in between interactions.
Of course, that all hinges on what you mean by the term "don't exist".  If what you mean to say is that between interactions, an electron is in a state we don't really understand, then you would find fewer people who disagreed with you. However, if you say that an electron 'doesn't exist' between interactions- most people would say you are going too far, as that implies that the electron's mass and charge stop existing, and there is no experimental evidence to support such a view.
