If you rolled marbles down a hill, assuming that identical starting conditions were applied each time, then the marbles' paths and final position would be the same each time.
This also implies that if you know the starting conditions, you could calculate the state of any point in time from there.
It made me curious whether you could apply this same logic to our universe -- though I get the feeling it's not quite as simple a system as marbles on a hill.
The Nature article and your comment reminds me of [1]: What if the hill is a perfectly symmetric hemisphere, so that every path down the hill is equally valid?
In fact, this is precisely the shuttlecock analogy in the Nature article, even though that analogy is talking about the quantum Universe initial boundary state, as opposed to the hemisphere example in classical Newtonian mechanics.
I guess the shuttlecock analogy isn’t that useful after all, since it fails to set apart quantum Universe theory from Newtonian mechanics, in that the latter can also have no boundary.
[1] The Dome: A Simple Violation of Determinism in Newtonian Mechanics
The fundamental question here is whether or not you can get identical conditions in the first place. If for example spacetime is quantized, then it might be that the basic unit of our reality displays the sort of quantum behavior that makes it so hard to predict outcomes. It wouldn't just be a complex system, it would be an essentially random and ever-changing system. By the same token it could be the opposite, maybe it's just a really complex system as you were speculating about, and while nothing is random, it's essentially impossible to predict.
In essence, is this a universe where a version of Maxwell's Daemon could conceivably exist, or is it a universe that even a god-like being would find random?
You can create a marble run and have marbles more or less follow the exact same path every time. However, on some scale there is an unpredictable nature to things like Brownian motion which affect the run in subtle ways. Perhaps you could get closer if you could account for the physical properties of every particle in the system beforehand, but a some scale these interactions are driven by quantum mechanical processes that aren't predictable even with perfect information (as far as we know).
To look at it another way, the entropy of a system is always increasing, so you don't have enough information when the marble is at the top of the hill to know the exact outcome when it's at the bottom (on a quantum scale, or over a long enough period of time).
If the path of the marbles were to be determined by some sort of gate in the path that would open or close depending, via a Geiger detector, on whether some uranium atom had decayed, then, as far as we know, the path would be truly unpredictable.
My mental model for this is to consider boiling water in a pot. You can make easy statements over how long it will take for all of the water to evaporate. It is, to my understanding, impossible to discuss any particular molecule or atom.
That is to say, the closer you get to the atomic behavior of atoms, the harder it is to make "deterministic" descriptions of what is going to happen.
We often describe this in terms of "coin flips" as you can make a decent discussion over what you will see on 1000 coin flips, but you cannot make such a statement over what you will see over 1.
i think for physical systems this might hold true in some way, though, i am not a physics person at all. it just 'feels' that way to me. however, life is also there, and life doesnt nessesarily follow such rules, as actually most of (intelligent?) life is not physical. (emotions, thought etc.) but does have impact / effect on the physical. i dont think non physical things are so determenistic. (maybe they are, but it doesnt 'feel' that way to me)
For classical physics it's basically true[1]; see Laplace's demon. I recall also independently inventing determinism as a kid after I realized how easily I'd been swayed by external factors into buying one toy over another.
For non-physical things, such as emotions and thought... well, we have no actual proof they're anything but physical. We just don't have proof that they're entirely physical, either. But the simplest explanation is actually that they are completely physical processes and just as deterministic as everything else (which is to say, possibly not at all, depending on how QM is resolved).
[1] "Basically true" here means it's not strictly true (by that I mean it's not true in all possible cases) - but classical physics itself is not strictly true, thus relativity and QM... which are themselves not strictly true. We're still trying to find the theory that accurately describes all of physics.
I disagree that it's the simplest explanation. The starting point is the mind, because it's what asks the question.
The physical world may or may not exist out there entirely independent of mind phenomena but the physical laws are a mental model in order to understand the world, the physical laws arise out of the interaction between the physical world and the mind.
The operating order is like this: there is mind -> mind perceives world -> mind makes mental model that presupposes the perceive world is independent of mind -> mind tries to determine its own origin within that presupposition.
If you simplify to the most extreme degree you're not left with "the physical laws", you're left with "there is mind". As such, the burden of proof is on the side of the presupposition that the external world is entirely independent of the mind that perceives it.
That's if you take an either or approach. One could also take the view that they're interdependent, there's no "mind causes matter" nor is there "matter causes mind" (or alternatively, both are simultaneously true).
When you imagine from your minds eye, that is a plane of some sort.
If we understood exactly where or how this plane exists and for whom, we could arbitrarily place objects and ideas in this plane. Eg force someone to think of a red ball bouncing, or pull imagined objects forcefully out of the plane.
You're asking me to define the physical nature of thought? Of subjective experience? I can't. No one can.
As I already said, though, that doesn't mean we should assume there's something metaphysical going on. When I think of a red ball neurons fire. We have no reason to believe there is anything else going on because we have no evidence one way or the other. The experience of thinking of a red ball is not evidence that there's anything supernatural going on.
Eg force someone to think of a red ball bouncing...
Indeed: put them in a sensory-deprivation tank and show them a video of a (possibly simulated) ball bouncing. Their existing network of neurons will do the rest.
There seems to be no reason to believe that it's not.
On the contrary it seems most plausible that everything, including emotions, thoughts, decisions, are just chemical and electrophysical reactions. Thus deterministic.
If you rolled marbles down a hill, assuming that identical starting conditions were applied each time, then the marbles' paths and final position would be the same each time.
This also implies that if you know the starting conditions, you could calculate the state of any point in time from there.
It made me curious whether you could apply this same logic to our universe -- though I get the feeling it's not quite as simple a system as marbles on a hill.