Comment by mkrecny | Hacker News Reader

Comment by mkrecny | Hacker News Reader

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And yet if a system is deterministic, it certainly is predictable (read: able to be predicted) and does lack free will. So if the universe is a deterministic automata the 'unsatisfactory dehumanizing implication' stands. Despite this, the only way to predict the state of a Conway system n iterations from now is to allow the system to run for n iterations. No one could actually model the universe precisely by creating a cellular automata. The automata would have to contain as much information as the universe, so it couldn't fit within the universe. Also even if the builder did know the system rules and a valid starting condition he could only compute as fast as 1 iteration per iteration of the actual universe...and hence not be able to outpace the universe and predict the future. I think solipsist is right about macro vs micro rules. And the macro rules themselves have macro rules ad infinitum. At some point you get to macro rules that try to describe human behavior (which apparently don't work very well). I don't think the cellular automata reductionist approach will help us too much in predicting the future in our universe for reasons mentioned above. We may be better off with macro rules like Newtonian physics and so forth.

By your parenthetical I assume you know of chaotic systems. But yeah, its been some time since I read philosophy but I vaguely remember that you still aren't guaranteed free will just cause things are undeterministic. This is because since you cannot show that an event was caused you cannot prove that your actions led to the event. How do you know that it is because of your actions that some event occurred or you chose to act as you did if things don't necessarily lead from one another? And the other side is true too. Just cause things are determined does not necessitate free will be lost. It was usually sugar coated but I always took it as even with just the illusion of free choice, that ability to be able to seemingly choose what you would have anyways is free will.

I stopped thinking about such things as I always got stuck in a head wrenching recursive loop of futility.

: ) yeah I know how you feel

Perfect explanation. I'm pretty sure that macro is the way to go. I have a theory that you can take anything and separate it into macro and micro levels (whether it be economics, science, etc.) You can look at systems at different scales and, while there is sometimes an intermediate, it's usually possible to separate the interpretations into two distinct categories.

As mkrecny stated, choosing to observe and predict the micro aspects of our universe is a lost cause. However, finding patterns in higher levels of systems is what makes science works. While micro systems are usually the areas left for theorists, macro systems have real life applications for scientists. We predict things every day and some things are simply easier to predict than others.

His explanation isn't perfect. It's quite flawed. Rice's theorem (and the more well-known halting problem) demonstrates that deterministic computation is absolutely unpredictable.

Not true. Determinism does not imply predictability where predictability means "able to be computed faster than just waiting for the algorithm to play out." When the whole universe is performing a computation, even if it's deterministic, there's no way to "predict" in the sense of knowing a future event before it takes place. Any other definition of "predictable" doesn't make sense.

An additional (and perhaps stronger) argument is that Rice's theorem states that you cannot in general predict the behavior of deterministic computation. You can't know if a program will ever access the network card, output a letter "A," halt, etc. even though all of these programs are known to be deterministic.

I don't think anyone is saying that we can create a cellular automata (or any computer) capable of simulating the entire universe. That doesn't mean that the universe can't be modeled as one. You can't simulate an Intel i5 CPU in realtime in Windows 7 running on an Intel i5, but that doesn't mean an i5 isn't deterministic.

As a side node, the potential richness and unpredictability of deterministic computations is a major theme of many works by Rudy Rucker. Any investigation of cellular automata will reveal the unpredictability of deterministic computation, which is essentially the whole point behind cellular automata.

I feel like you stopped reading after the first sentence as we ended up saying the same thing. I certainly don't mean to say that determinism implies predictability in the first sense you define above. In the second, more general sense "knowing a future event before it takes place" predictability really could depend on the concept of emergence (or solipsists notion of macro-levels). Here's a thought experiment: It's conceivable that you could perfectly simulate a higher level of organization in a system (which would require less information). It's also conceivable that objects on that level (emergent properties of the lower levels) operate according to their own rules distinct from (but derived from) the lower levels. Here's the kicker: given that the higher level is an emergent property of the behavior of the lower level, when we look at it in isolation, it contains much less information than the lower level. In fact several state iterations of the lower level could pass before a state change percolates to the higer level. Thus, in such a thought experiment by having a perfect model of the higher level, you could outpace the lower level and know a future even before it takes place.

It does not follow that a deterministic system is predictable, depending on what you mean by "predictable", in theory or in practice. A Turing machine is deterministic, but predicting whether it will halt or not is not decidable.

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