Is the future inevitable?

In a deterministic universe yes. Otherwise no.

What I cannot fathom is how any event can happen without a preceding event.

I guess that before causality was invented lots of things just 'happened'.

Yes, events do have preceding events. No one is saying otherwise. But, in a probabilistic universe, if you wind the clock back far enough from that event and start over the play out of the probabilities on the second run may not produce the same event from the first run. Whatever different event does happen on the second run will, of course, have had a different set of preceding events.

I think that the point of chaos is that it magnifies the effects of random events. Small chance fluctuations in a non-chaotic universe would take much longer to have a significant effect.It would also magnify the effects of very small differences, so an apparently but not exactly identical universe would also tend to diverge from ours.

Clockworks always play out the same way and so we can predict the position of the clock at some future time with precision. We use probabilities to predict outcomes for events that we do not have all of the variables for like nuclear decay.

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So, for example, according to QM the fullest description possible of a radium atom (or a chunk of radium, for that matter), does not suffice to determine when a given atom will decay, nor how many atoms in the chunk will have decayed at any given time. The theory gives only the probabilities for a decay (or a number of decays) to happen within a given span of time. Einstein and others perhaps thought that this was a defect of the theory that should eventually be removed, by a supplemental hidden variable theory[6] that restores determinism; but subsequent work showed that no such hidden variables account could exist. At the microscopic level the world is ultimately mysterious and chancy. Source

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I guess my question is how do you prove that no hidden variables exist?

I would think that quantum effects would cause the states of two universes that began in identical states to diverge. At the quantum level particles will flit in and out of existence, but not identically in the two universes. Eventually and inevitably these quantum differences will manifest themselves at the macro observable level.--Percy

Not necessarily. It's possible to make certain small changes to a chaotic system without altering the outcome at all. A slightly different small change, however, could have dramatic effects, but it is theoretically possible to have two slightly different universes which are indistinguishable (once again, I'm ignoring quantumness (quantumity?)).Edited by caffeine, : No reason given.

This question has come up before and we got some answers back when cavediver and Son Goku used to post here regularly. Here is a partial answer:Bell's theorem - Wikipedia

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Bell's theorem states that any physical theory that incorporates local realism cannot reproduce all the predictions of quantum mechanical theory. Because numerous experiments agree with the predictions of quantum mechanical theory, and show differences between correlations that could not be explained by local hidden variables, the experimental results have been taken by many as refuting the concept of local realism as an explanation of the physical phenomena under test. For a hidden variable theory, if Bell's conditions are correct, the results that agree with quantum mechanical theory appear to indicate superluminal effects, in contradiction to the principle of locality.

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Are you sure about that? QM and GR might disagree. Hidden variables has been a contentious point with QM since Einstein and the EPR paradox. But, the worm has turned, as they say, and the present consensus is hidden variables do not exist. The Bell Inequities, Alain Aspect's and Nicolas Gisin's experiments show that hidden variables has some fatal flaws that preclude their reality.One does not prove that hidden variables do not or cannot exist. One can only show the preponderance of the evidence is against such things.IMO one of the best, comprehensive and lay-friendly write ups on whole controversy is here

Yes I know. In my defense, the answers are described as counter-intuitive even by those who provide them. Causality seems so necessary. An object at rest will remain at rest.I find it easier to accept the idea that distance is an illusion as opposed to the idea that things happen without cause.

Im still trying to wrap my mind around the concept of determinism versus random probability. I dont think I believe in an either/or throw of the dice. I believe that the throw has been determined by a hypothetical observer.Please help me.

You know the seeds of sychamore trees have little wings on them? They allow the tree to spread its seeds a distance from the mother tree. They get dispersed by the wind sometimes for hundreds of yards. Some of them land in roof gutters, car parks and roads, some get eaten by squirrels, some of them drown in lakes. Some of them get carried down river miles away from the tree.Do you believe that where each individual seed lands has been preditermined?Or do you think it more likely that that can not be true given the enormous number of variables involved - almost all of which are random and/or chaotic.

only if any one variable is no more or less influential than any other variable.

Eh?