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I was curious as to whether there are any philosophical issues discussed with this concept. Note that by an indefinite reality (and I may be using the wrong term), I mean the notion of reality having an inherently probabilistic/indefinite state.

For example, entangled particles in quantum mechanics are said to have indefinite states before measurement. So what I’m curious about is this: at each moment, if the state of a particular particle is defined as indefinite in its mathematical formalism, how does this look like from an ontological perspective?

Assuming a single world and not multiple worlds where each possibility simply gets realized which seems easier to conceptualize, what does superposition in a single world imply with regards to ontology? Is a particle literally at two places at once before measurement? Is it in a haze like form with respect to each possibility such that it becomes two particles for the time being? The first seems contradictory and the second seems vague and weird. Is there another option or do we simply not know the answer to this question?

What I find difficult to do is to conceptualize any form of inherent randomness with respect to underlying ontology unless it becomes so vague that it becomes meaningless to even talk about, especially with regards to the Copenhagen interpretation of quantum mechanics.

Of course, the universe doesn’t have to care about what humans can or cannot conceptualize. And of course, applying ordinary intuitions to the subatomic field may not be the answer. But what is the replacement? Usually, when intuitions are disproven, there is a replacing ontology. After reading about some of the interpretations of quantum mechanics, it seems like it just gets rid of the ontological question altogether and gets rid of it. Could it be the case that the very difficulty with mapping true randomness to an ontology is a sort of indication that it may not actually describe reality as it is? Or no?

Are there any papers that specifically talk about how the ontology of true randomness can look like? Are there any concerns with the logical possibility/impossibility of this concept?

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  • Quantum physics, computer simulation and AI - they are modern killers of traditional philosophy. You would not find too many suicidal academics willing to write on this subject. Commented Apr 6 at 2:28
  • The system state is perfectly definite in the mathematical formalism, it is from attempts to reduce it to familiar images, like particles, that problems come from. As with all analogical imagery, one should expect that many questions it suggests are nonsensical. "Quantum particles" are not particles, there are no particles there to be two places or one place. Nonetheless, "in fact it seems that a reasonably sensible, indeed, an almost off-the-shelf, ontology is available to the quantum Bayesian", Timmons, Quantum Bayesianism, p. 22ff.
    – Conifold
    Commented Apr 6 at 3:08
  • @Conifold An example of quantum entanglement involves photons that are detected at measurement. In the case of two photons being entangled, what exactly is happening to one of those photons before measurement? Do they cease to exist? What do you mean when you say there are no particles there in this case? Commented Apr 6 at 3:15
  • If you do not know what it means that there are no classical particles in QM, then you should start there before venturing into ontology. The state is described by the wave function, the rest is metaphorical language that applies even roughly only to measurement-like interactions. "What is happening to one of those photons before measurement" is a nonsensical question. Little ball associations and questions they bring up will only mislead you in QM.
    – Conifold
    Commented Apr 6 at 3:51
  • I’m not making the claim that there are classical particles in QM. I’m asking what is “there, as a matter of reality” before measurement? You can call it whatever you want, I’m simply asking what exactly is happening to the photon (which is a particle, which is all I said) before measurement? If this is a nonsensical question, then what else is happening? I’m not sure how it is nonsensical to ask what is going on in reality before measurement especially since many other physicists have asked the same question Commented Apr 6 at 4:14

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It depends on quantum interpretation. Each interpretation fixes some philosophical non-intuitive issues while introducing others.

Particularly, Copenhagen interpretation says that there is no sense to talk about "position of a particle" or its trajectory. Instead, the system is fully described by the spatial distribution of the wave-function of the particles. There is no particle. There is a wavefunction, a kind of field. It undergoes deterministic (non-random) evolution until the wavefunction collapses during measurement.

Another interpretation, de Brogle-Bohm one, says that the particle in fact has a trajectory and moves absolutely deterministically. The only source of apparent randomness in observation is due to unknown initial conditions of the universe.

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