I feel that QM and the Copenhagen Interpretation are of great value regardless of whether realism is true or not, so I am going to challenge some of Mmfiore's statements for the sake of better elucidating and representing QM and CI, not to try to discredit realism. (I may eventually have to take on realism, however, depending on where the discussion goes).
I believe at the very fundamental level of matter and energy the answer can be obtained by looking closely at isolated atoms and observing them. This is a way we may be able to disprove QM. I believe that studying a system suspended in isolation will reveal a deterministic chaotic system not a random one. The problem we have now in the subatomic realm is that simple deterministic laws of Newtonian mechanics can generate very complicated and yes even random motion. In the past we have tried to study systems in experiments that are very complex at the sub atomic level. These systems are so unstable that trying to observe and determine the course of trajectories in the subatomic realm is impossible using the techniques and technology currently available. The problem we now have is that even in the simplest of systems the trajectory of objects in the system is highly dependent on the boundary that confines the system. In quantum systems the boundaries are highly irregular and dynamic. This will make it impossible for us to use classical equations to predict anything.
Here’s the catch, in Quantum Mechanics an isolated atomic system cannot take any value as it could in classical physics. Therefore I believe that this means that a simple system according to QM will be restricted to a set of possible energy levels. So when we perform an experiment and analyze the experiment using a set of Quantum Mechanics equations which employ the use of Schrodinger’s equation we can calculate with great accuracy the probabilities of a certain event occurring (the Measurement). The bottom line is this, Quantum Randomness lies not in the waves but in the process the waves describe. QM is purely statistical analysis with a fine tuning element (Schrodinger’s wave equation) as all particles and systems have a wave component. QM is just a real good tool for analyzing the sub-atomic realm. There is nothing in this process that explains how the particles move. There is nothing in this process that even explains why particles move. There is nothing in this process that explains how a particle gets from location (a) to location (b) or at what speed, certainly not both at the same time. QM cannot even explain why the speed of light is the exact value it is. Ah, but when we do experiments involving particles in the microscopic realm we did get the right answer.
I'm assuming that "the right answer" in this context means precise values (the corresponding probability equals unity, i.e., 100%) as opposed to the spread of probabilities presented by Schrodinger wave mechanics. If that is what you mean, then I mostly agree with these statements except for there being any "catch." QM is a model that works differently than a Newtonian model. To my mind, the idea that QM has "lost" the ability to compute precise values that Newton and Maxwell offered is like saying we lost the "warm analog sound" when we switched from analog to digital music production. Digital music offers so much that analog was incapable of, even though some people interpret its clarity as "brittle." Likewise, QM lets us understand subatomic behavior in ways that have given us amazing insights and technology, even though some people interpret its counterintuitive/probalistic view of matter & energy as "incomplete." So it's convenient to let audiofiles listen to 180-gram virgin vinyl when they want while others pop on their ear-buds for an MP3 file. So it's convenient to model tables, chairs, and planetary orbits via Newton while particle physicists use a different model to more readily interpret their observations.
How can we use probability as the basis for our reality at any level?
QM doesn't use probability as "the basis for our reality." It uses it to model subatomic behavior. It chooses not to investigate beyond the probabilities because it has no scientific methodology for doing so that is derivable or implied by its existing formalism.
Probability is the chance that something will happen. A chance does not provide the basis for force. A chance does not provide the basis for the existence of physical objects that we observe in the macroscopic world or the microscopic world. Chance does not make the photon travel at the speed of light. Chance does not help us at all in understanding 3 dimensional space.
You are correct, and the upshot could be that chance should be left to what it can explain. Personally, if I want to understand how subatomic behavior is going to conceptually link up with macroscopic behavior, I let QM alone and look to complexity theory. Emergence is a wonderful model for understanding how lower-order complexity and randomness generates higher-level simplicity and order.
Imagine a thrown ball from a pitcher. The ball is composed entirely of particles that according to QM are controlled by randomness. This according to the logic of QM should mean that to some extent the ball should be somewhat unpredictable in its flight. Yet the entire collection of particles of which the ball is made of travel in a completely predictable trajectory described by classical mechanics. If the ball which is nothing more than a large pile of quantum objects can behave in a non-random means does that not imply that in order for this to happen each and every particle in the ball must be adhering to classical laws and not probabilities?
No, that is not implied, because you are ignoring the phenomenon known as
decoherence. You cannot arbitrarily ignore that the presence of the quadrillions of overlapping wave functions inherent in the modelling of a baseball's quanta are interacting, amalgamating into what is sometimes referred to as a Schrodinger Pulse, most of which is constituted by the cancellation of most of the waves' extremes of amplitude, resulting in an overall wave function for the baseball that is so tightly bounded, that the probability of that baseball displaying any macroscopically visible quantum effects is virtually nil. (There are other ways for QM to model this, such as Feynman's sum-over-histories approach). The very existence of macroscopic phenomena implies decoherence, given that they are indeed made up of quanta capable only of quantum mechanical behavior.
More interesting to me is that even if one could truly calculate the wave functions of every quantum in a baseball, you could in principle reach a set of results that describe the Schrödinger pulse, but
nowhere would the baseball per se be evident as a discreet entity. Indeed, such a quantum-level analysis would have a difficult time isolating where the quanta of the baseball end and the surrounding air begins. This is why we have multiple models of reality. The macroscopic world displays emergent properties better modeled by complexity theory than QM.
Probability is something that we have dreamed up. It is a mathematical abstraction with no physical existence. The only reason probability exists at all is that we need something to help us be better at guessing. It’s not good science.
Given its record for accurate prediction, probability is actually excellent science so long as we continue to believe that it is indeed a mathematical abstraction with no physical existence. The Copenhagen Interpretation says in effect, "Randomness is the baseline for physics." It does NOT say that "Randomness is the fundamental metaphysical principle of reality." There is HUGE difference between these 2 statements, conceptually, philosophically, scientifically, and practically.
Once we can theorize properly (hypotheses with testable conclusions) about what is behind the probability--instead of stretching inappropriate models into areas where they don't belong (i.e., cannot yield testable conclusions)--then I will agree that to uphold probability as the baseline for physics is no longer good science. Until then, I think Bohr is being responsible to science when he says, "Physics is what we can say about nature."