I've been interested in physics since I was a kid, and read many books on the topic. The thought experiments of Einstein that led to his theories of relativity were some of the earliest topics I encountered. If you have not read of that, do so . . . I will wait.
So we come to the EPR paradox. The new field of quantum mechanics in the 1920s presented this conundrum - that particles could have entangled properties but that those properties would not become determined until a measurement event, at least according to Bohr. But upon one measurement, both particles states would be determined even if they were separated, and this determination would be instantaneous - faster than light.
The EPR paradox received further attention in the 1950s and led to the Bell's Inequalities - describing the paradox in some detail. Bell proposed solutions to the paradox which are each a bitter pill in their own way. Some have received greater press, but there is nothing yet known to choose among them. Two that are most conspicuous are 1) a multiverse - all the outcomes exist in separate parallel universes, and 2) hard determinism - the paradox arises from quantum mechanics being predictive, but spacetime is complete and only one outcome actually exists - always has and always will.
The more I have thought on these options, the less possibility I can grasp for matters spiritual. The multiverse scenario seems ridiculously uneconomical to my admittedly-Calvinist upbringing, but if all outcomes exist, what judgement can there be for how a person lives (i.e. we live in ALL the ways we can). The hard determinism scenario is crystalline. We do not actually have any free will whatsoever - not even the free will to take advantage of being completely inculpable for our actions.
I think there may be a more mystical way of thinking of hard determinism though - a koan, if you will. We are agents of causality within a complete four-dimensional spacetime. We bring the crystalline structure of the universe into existence by virtue of our own existence in some way.
Right, I was saying a quantum 90%/10% coin as shorthand for something like "arrange a magnetic field in z+ direction, shoot electrons through it, collecting those that deflect in direction consistent with spin up, then, without disturbing the electrons otherwise, shoot them through a second magnetic field inclined 28.8° away from z+ and count the number spin-up vs. spin-down". Specifically to avoid getting distracted by questions like whether a cointoss is quantum-random or merely mechanically-random. Sorry if that wasn't clear.
in your quantum multiverse, there is an important distinction to be made between mechanically-random and quantum-random; but in my hard-deterministic universe, the distinction, while maybe of some metaphysical interest - is immaterial, since both mechanisms are striving to predict an inescapable outcome. ;)
Ok, so why did you even bring up quantum in the first place? I thought you wanted to talk about EPR and Bell inequalities, but you were just focused on hard determinism?
Forget the quantum coin. Let's use a regular 6-sided die. No quantum woohoo. You pick: sixes or not sixes? We roll the die, if you guess right I give you a dollar, if you guess wrong you give me a dollar. We'll keep rolling until you run out of money or I grow bored.
You say you are living in block time and all rolls, past present and future, are already predetermined and nothing you can do or choose will change that. Whatever you pick, it doesn't affect your probability of winning, because there is no probability - either you were already destined to win on the next roll, or you were destined to lose. Indeed your pick itself was pre-determined and you have no free will to consider one choice over another.
So here, I'll make the choice for you. Before we start our game, I'll give you one dollar for free if you make a commitment to always pick sixes. This is a strict advantage for you, because regardless of your future wins and loses (which you can't influence), you'll always at least have this extra dollar.
Ready to play?
This is what I find so interesting about the topic! Hard determinism is constrained by causality. Although the future is fixed, the events that transpire are causally linked to the past, and we seem like active agents of decisions. So since I am not a gambler, I never participate in wagers even though the outcomes are predetermined (or in my case the lack of wagers is predetermined). We are having this discussion in the context of the atheism community, so I think it is worth mentioning that there seems to not be much space in either hard determinism or a multiverse for the sort of spiritual-guidance and enforcement mechanisms proposed by religions. And yet, there may be a kind of mysticism to ponder whether we consider ourselves a more or less thick outcome slice, or whether we are agents of cause in a predetermined block time.
Did I bring up quantum? Well, if I did it was in the context of explaining Bell's "solutions" to the EPR paradox. He thought there were three, as I recall, and he ruled one of those out. He ruled out hidden variable. So multiverse or hard determinism were all he had left. He did not care for hard determinism but he did not say why, as far as I know.
I knew you were going to say this!
Do you know how I know? Because that's the problem with hard-determinists - deep down you don't really believe it. In your mind you have calculated the probabilities you claim don't exist, and in your heart you fear I would clean you out. And you are damn right I would! That's why I sweetened the deal by paying you one dollar up front. This way, choosing to play the game is a dominant strategy... for you. I'm not a gambler myself, never have gambled in my life, but if some crazy-but-honest hard-determinist millionaire offered me this sixes game, and paid me on top of that to commit to not-sixes, I would jump into it in a heartbeat. If you truly believed, you would have no fear.
In real life you don't get the privilege not to gamble. You gamble every time you take an umbrella (or not) when going outside. You gamble every time you cross the street. Every action you take is guided by frequentist thinking. And this one time you just completely arbitrarily in a pre-determined way "decided" not to play my game? Ha! I have predicted this. So much for the future being determined but unpredictable!