Is free will possible in a deterministic universe?

[Write4U]

I was not talking about reversibility, but from what I read online, it seems that all of quantum mechanics is fully reversible.

Perhaps theoretically as a way to reconstruct deterministic progressions, but I really doubt anything is physically reversible.

I was speaking of determinism, and reversibility does not follow from determinism. Conway's Game of Life for instance is fully deterministic, yet is not reversible.

Theoretically it is, practically it is not. Looks to me it is based on chaos theory. As long as we have all the information we can theoretically trace back its forward progression, no? We just cannot back engineer a hurricane to the flapping of butterfly wings, but if all the information was available we could mathematically trace it back to the beginning, else we could not make that assertion in the first place.

But bringing a dead thing back to life going backward in time is another matter.

I thought pilot wave theory had pretty much been falsified.

Well AFAIK, no more so than the Copenhagen Interpretation. It just requires one additional assumption, but then yields a perfectly deterministic system without the very problematic assumption of particle duality.

Many physicists pay lip service to the Copenhagen interpretation—that quantum mechanics is fundamentally about observation or results of measurement. But it is becoming increasingly difficult to find any who, when pressed, will defend this interpretation.

It seems clear that quantum mechanics is fundamentally about atoms and electrons, quarks and strings, not those particular macroscopic regularities associated with what we call measurements of the properties of these things. But if these entities are not somehow identified with the wave function itself—and if talk of them is not merely shorthand for elaborate statements about measurements—then where are they to be found in the quantum description?

But in 1952 I saw the impossible done. It was in papers by David Bohm. Bohm showed explicitly how parameters could indeed be introduced, into nonrelativistic wave mechanics, with the help of which the indeterministic description could be transformed into a deterministic one. More importantly, in my opinion, the subjectivity of the orthodox version, the necessary reference to the “observer”, could be eliminated. …

But why then had Born not told me of this “pilot wave”? If only to point out what was wrong with it? Why did von Neumann not consider it? More extraordinarily, why did people go on producing “impossibility” proofs, after 1952, and as recently as 1978? … Why is the pilot wave picture ignored in text books? Should it not be taught, not as the only way, but as an antidote to the prevailing complacency? To show us that vagueness, subjectivity, and indeterminism, are not forced on us by experimental facts, but by deliberate theoretical choice? (Bell 1982, reprinted in 1987c: 160)

https://plato.stanford.edu/entries/qm-bohm/

I get the impression from cursory reading that Bohmian Mechanics was rediscovered and is alive and well in many scientific circles. I understand that is doesn't really make much difference, being that neither theory can be fully confirmed or fully falsified.

But I admit this way above my area of knowledge.....

 

[Sarkus]

Perhaps theoretically as a way to reconstruct deterministic progressions, but I really doubt anything is reversible.

The deterministic system of adding one to the previous state/number is entirely time-reversible. At least, I trust you can count forwards and backwards?

Theoretically it is, practically it is not. Looks to me it is based on chaos theory. As long as we have all the information we can theoretically trace back its forward progression, no?

No, even theoretically Conway’s Game of Life is not a reversible system. Many patterns conclude to nothing, so any pattern where all the cells are dead has many possible predecessors. You end up with an indeterministic system that relies on input external to the system, or the luck of randomness, to get the system back to where it started from. That makes it non-reversible.

We cannot back engineer a hurricane to the flapping of butterfly wings, but if all the information was available we could mathematically trace it back to the beginning, else we could not make that assertion in the first place.

No one has ever made that assertion, or at least not without misunderstanding what was originally asserted. The assertion was that, after a tiny change in the initial input of a predictive model had a significant effect on the output (notably where a hurricane would make landfall), the size of the change was jokingly compared to be like a butterfly flapping its wing.
But you are also again making the mistake of assuming that a deterministic system is necessarily reversible. They aren’t. Any deterministic system where two different inputs can both ultimately lead to the same future state is irreversible.
Here’s a mathematical example: consider the deterministic system of the next state being the square of the previous. If you start with -1 or 1, the system is quickly, if not instantly, in equilibrium. A number between them and it asymptotes to zero. Anything above 1 or lower than -1 and it grows exponentially. Agreed?
So, let’s reverse it: start with 625. What’s the next number in this reversed sequence? And the next? If you said 25, then 5, you are presuming that the system is limited to positive numbers. After all, the square root of 625 is + or - 25.
Thus it is time-irreversible: a state, as you head back in time, does not have a single possible preceding state.

 

[Write4U]

The deterministic system of adding one to the previous state/number is entirely time-reversible. At least, I trust you can count forwards and backwards?

I agree in theory. Physically no.

But what is curious, after you, make this statement about determinism, you immediately begin with falsifying the very process.

I believe that the definition of determinism always includes the qualification; "if all factors are known". That includes any and all separate historical equivalencies which may yield same results. It may be necessary to follow several historical paths, but eventually you will find the actual chronology.

But you are also again making the mistake of assuming that a deterministic system is necessarily reversible. They aren’t. Any deterministic system where two different inputs can both ultimately lead to the same future state is irreversible.

But you are assuming that we are unable to retrace "every" history of every causal input. i.o.w. theoretically there are no "unknowns" which can yield similar result from different equations. Then the expression "if all factors are known" would be misleading, no?

 

[Halc]

Theoretically it is, practically it is not.

Practicality has nothing to do with the subject being discussed. A system is said to be reversible if the mathematics describing its behavior is 1) deterministic, and 2) time symmetric. CGoL is not time symmetric.

Looks to me it is based on chaos theory.

A chaotic system might still be deterministic.

As long as we have all the information we can theoretically trace back its forward progression, no? We just cannot back engineer a hurricane to the flapping of butterfly wings, but if all the information was available we could mathematically trace it back to the beginning, else we could not make that assertion in the first place.

It is impossible for humans to have this information (hence the answer given by Sarkus). RSF interpretation is local and completely deterministic, but any outcome of a system is in superposition, so a prediction of hurricane cannot be made. Bohm has defined state, but even a perfect description of that (including hidden variables) is not enough since it allows effects due to causes in the future, so the cause of the hurricane is potentially due to events that take place after the hurricane.

I thought pilot wave theory had pretty much been falsified.

Well AFAIK, no more so than the Copenhagen Interpretation.

Copenhagen interpretation is not deterministic, but other interpretations are. Copenhagen is an epistemological interpretation, and has not been falsified.
Some take it as a metaphysical interpretation, but that stance is what is becoming increasing difficult to defend. It was never meant to be a metaphysical interpretation by its authors.

I get the impression from cursory reading that Bohmian Mechanics was rediscovered and is alive and well in many scientific circles.

It very much is, yes. They just abandoned the pilot wave model AFAIK.

I believe that the definition of determinism always includes the qualification; "if all factors are known".

The time symmetry of a mathematical model has nothing to do with knowledge of the factors. Said knowledge is needed to make accurate predictions, but not to note the property of time symmetry of a model. So the universe may possibly be fully deterministic, but it has been shown to be impossible to predict the outcome of even the most trivial experiment like when a given nucleus will decay. Such is the difference between determinism and predictability.

 

[Sarkus]

I agree in theory. Physically no.

Physically you can't count forwards and/or backwards???
As Halc as said, it is the definition of reversible, and to use his words: "A system is said to be reversible if the mathematics describing its behavior is 1) deterministic, and 2) time symmetric."

But what is curious, after you, make this statement about determinism, you immediately begin with falsifying the very process.

No I don't. I have not said that all deterministic systems are reversible, but did give an example of a deterministic system that is. All reversible systems are deterministic, but not all deterministic systems are reversible.

I believe that the definition of determinism always includes the qualification; "if all factors are known".

Nope, that's merely an attempt to clarify the practical limitations of prediction of a deterministic system. Determinism is usually defined in terms of the effect being wholly determined by the cause. Knowledge of a system is irrelevant to whether it is deterministic or not, only relevant to predictability.
To clarify: a deterministic system is theoretically predictable with certainty "if all factors are known" about any input plus the governing laws. If you don't know all the factors (a matter of what is practical), the system is still deterministic but you just won't be able to predict with certainty.

That includes any and all separate historical equivalencies which may yield same results. It may be necessary to follow several historical paths, but eventually you will find the actual chronology.

That depends on the system. We have given you one: Conway's Game of Life: deterministic in one direction only, since multiple different inputs can lead to the same output, thus when reversed you end up with one input having many possible outputs. This makes it deterministic in one direction and indeterministic in reverse.

But you are assuming that we are unable to retrace "every" history of every causal input. i.o.w. theoretically there are no "unknowns" which can yield similar result from different equations. Then the expression "if all factors are known" would be misleading, no?

Knowing "every history of every causal input" is not part of what is required for determinism. That is what is meant by omniscience, surely. Theoretically, though, a deterministic system that is time reversible can provide omniscience - i.e. if you know everything about just one state/input plus the governing laws then you could know every state in both the forward and backward direction.
But please understand that determinism has nothing to do with knowledge, but that perfect knowledge of a deterministic system at any given time/state does allow perfect prediction going forward, and only perfect prediction going back in time if the system in question is time-reversible.

 

[Write4U]

Physically you can't count forwards and/or backwards???

Oh I can count forwards and backwards and standing on my head . But I cannot ever count backwards in time, no matter how I count it is always forward in time, due to the fact that time emerges with the action of counting and is irreversible. Hence time is irreversibly uni-directional.

Time is the indefinite continued progress of existence and events that occur in an apparently irreversible succession from the past, through the present, into the future.

https://en.wikipedia.org/wiki/Time

As to determinism, I'll concede to you, who has obviously much greater knowledge of the subject than I do. I do reserve the right to address the subject at a later time....

 

[Sarkus]

Oh I can count forwards and backwards and standing on my head . But I cannot ever count backwards in time, no matter how I count it is always forward in time, due to the fact that time emerges with the action of counting and is irreversible. Hence time is irreversibly uni-directional. https://en.wikipedia.org/wiki/Time

Noone is talking about whether time is uni-directional or not. We are talking about systems and whether they are [url=https://en.wikipedia.org/wiki/Time_reversibility]time-reversible or not. Being time-reversible is simply a property of the governing laws/rules of the system, nothing per se to do with whether time can run backwards. It is more a case of the nature of the system if time ran backwards... not that it necessarily could. [/URL]

Whether time itself is reversible or not is somewhat of a metaphysical issue, wrapped up with the question of what time itself is. Your quote from wiki clearly indicates that it is "apparently" irreversible, but that speaks much more to our perception of time than to what time actually is, or how it behaves.

As to determinism, I'll concede to you, who has obviously much greater knowledge of the subject than I do. I do reserve the right to address the subject at a later time....

You quote wiki often enough, you just need to start there.

 

[Write4U]

Whether time itself is reversible or not is somewhat of a metaphysical issue, wrapped up with the question of what time itself is.

I was using this in context of reversal of deterministic systems. If time is not reversible then all speculation about proof of determinism is moot and can only be addressed as theory.

Your quote from wiki clearly indicates that it is "apparently" irreversible, but that speaks much more to our perception of time than to what time actually is, or how it behaves.

See, I read this as an affirmation of at least the appearance of irreversibility. If it was the reverse it would have said "apparently reversible". You cannot use a positive statement to prove an opposite. If it says; "apparently irreversible", I take that to mean it that here is no evidence to the contrary. Hence all discussion of reversing time to investigate determinism has to be theoretical only, thus any statement which proposes a variety of indeterminate deterministic functions can only be treated as theory, no?

p.s . I believe in a mathematical universe, which only processes relative values via mathematical functions,
regardless of human symbolic languages. IMO, this cannot yield anything other than a mathematically deterministic universe.

 

[Sarkus]

I was using this in context of reversal of deterministic systems. If time is not reversible then all speculation about proof of determinism is moot and can only be addressed as theory.

Who is speculating about proving determinism here??? I'm merely explaining that while all time-reversible systems are deterministic, not all deterministic systems are time-reversible, which you seemed to be somewhat confused about.

See, I read this as an affirmation of at least the appearance of irreversibility.

Correct. The "appearance of irreversibility".

If it was the reverse it would have said "apparently reversible".

And if it was an egg it would undoubtedly have been described as such as well.

You cannot use a positive statement to prove an opposite.

I'll bear that in mind should I ever find myself even considering it. But alas that isn't the case here.

If it says; "apparently irreversible", I take that to mean it that here is no evidence to the contrary.

Correct. That is how I take it, but also that it accepts that we don't really know for sure and the the position we do take is based on appearance - e.g. our experience and perception of it - rather than knowing what it actually is.

Hence all discussion of reversing time to investigate determinism has to be theoretical only, thus any statement which proposes a variety of indeterminate deterministic functions can only be treated as theory, no?

There is no such thing as an indeteminate deterministic function... it is an oxymoron. Either a function is deterministic or it is not.
But yes, this is all philosophy. Metaphysics, even. I was merely trying to correct you on a mistake you were making with regarding your understanding of deterministic systems: that is, not all are time-reversible. If you have a deterministic system X, and you know the state of the system at X100 and the governing laws/rules, then the nature of determinism is such that you can know every future state with certainty. That is not a definition of determinism, but it follows from what determinism is.
However, only if that deterministic system is time-reversible could you also know with certainty every moment of the system prior to X100 as well. If the system is not time-reversible then you can not know every moment.

p.s . I believe in a mathematical universe, which only processes relative values via mathematical functions,
regardless of human symbolic languages. IMO, this cannot yield anything other than a mathematically deterministic universe.

Alas the universe is not deterministic, though. It is probabilistic at best. This is almost universally accepted. Some interpretations of QM allow the universe to be deterministic, but only when considering the multiverse (many worlds), but at the local universe level there is then no way of knowing which universe you are actually in, thus you end up in the same position as the indeterministic (probabilistic) universe, just calling it something different by assuming other universes exist. And if QM is inherently probabilistic, that's okay for a mathematical universe which can cope with probabilities, but it rather puts a dampener on it being deterministic.

 

[Write4U]

Who is speculating about proving determinism here??? I'm merely explaining that while all time-reversible systems are deterministic, not all deterministic systems are time-reversible, which you seemed to be somewhat confused about.

I am confused about your use of the the term "time-reversible systems", when the definition of time states that it "appears to be irreversible". To me that presents a direct contradiction.

 

[Michael 345]

Whether time itself is reversible or not is somewhat of a metaphysical issue, wrapped up with the question of what time itself is.

A complex item can be disassembled and reassembled in what would be called a reversible operation

However the period over which the operation is not reversible because the period no longer exists

Or as I contend TIME does not exist

 

[Sarkus]

I am confused about your use of the the term "time-reversible systems", when the definition of time states that it "appears to be irreversible". To me that presents a direct contradiction.

You shouldn't be, as I gave a link to the wiki page on the notion of "Time Reversible". Look it up.

 

[Write4U]

You shouldn't be, as I gave a link to the wiki page on the notion of "Time Reversible". Look it up.

I understand the theorical (mathematical) value of imaginary time-reversal which allows for backward tracing of "effect from cause", but it cannot be done in real time, which is always uni-directional, and you cannot simulataneously go forward and backward in time.

That would literally and physically stretch you apart as in a black hole, where the front end of your body travels faster than the back end. And that is even going forward in time. Now imagine going simultaneously forward and backward in time.

But then, I don't believe actual physical backward time travel is possible at all, there is always that pesky uni-directional emergence of time which does not allow going back in time and undoing that which has already happened and completely restoring all the spacetime coordinates in a past moment, let alone duration. That creates an instantaneous natural paradox, IMO. We can look into, but never physically touch or undo the past.

Is there any hint of anyone ever having physically traveled back just 1 second in time or having reversed time in the physical world? I love theory, but theory has a much greater imaginary application than mathematical physical reality.

The universe has very practical evolutionary processes. You can never undo "natural selection'' of any physical process. But I'm open to demonstrated correction.

 

[Sarkus]

I understand the theorical (mathematical) value of imaginary time-reversal which allows for backward tracing of "effect from cause", but it cannot be done in real time, which is always uni-directional, and you cannot simulataneously go forward and backward in time.

Maybe I’ve missed something, but no one has suggested that it is possible to run time in reverse, to time travel, or anything else you’re complaining about. Whatever time is, and whether it is uni-directional, whether in actuality or merely in appearance/experience, I’ll leave to those discussing the metaphysics of the time. Here, as explained, I’m merely pointing out to you your error in assuming that knowing absolutely the state of a deterministic system at a given point is sufficient to know every state in its past. It isn’t, unless that system is also time-reversible. I.e. all time-reversible systems are deterministic, but not all deterministic systems are time-reversible. It’s as simple as that.
Why you are trying to muddle the notion of time-reversibility of systems with practical time travel, I have no idea.

As for whether time has reversed in the natural world, no one would ever know unless it only happened on a local level with forward-time available as a comparative. If it happened on a universal level, and the universe was a time-reversible system, you’d simply never know, any more than characters in a movie know if you’re fast-forwarding them, or playing them in reverse.
But all that has no bearing on the matter, and is better suited to a thread about the nature of time.

 

[Write4U]

Maybe I’ve missed something, but no one has suggested that it is possible to run time in reverse, to time travel, or anything else you’re complaining about. Whatever time is, and whether it is uni-directional, whether in actuality or merely in appearance/experience, I’ll leave to those discussing the metaphysics of the time. Here, as explained, I’m merely pointing out to you your error in assuming that knowing absolutely the state of a deterministic system at a given point is sufficient to know every state in its past. It isn’t, unless that system is also time-reversible. I.e. all time-reversible systems are deterministic, but not all deterministic systems are time-reversible. It’s as simple as that.
Why you are trying to muddle the notion of time-reversibility of systems with practical time travel, I have no idea.

Just trying to sort it out in my own mind. What may seem as a definitive statement is often only probative....

As for whether time has reversed in the natural world, no one would ever know unless it only happened on a local level with forward-time available as a comparative. If it happened on a universal level, and the universe was a time-reversible system, you’d simply never know, any more than characters in a movie know if you’re fast-forwarding them, or playing them in reverse.
But all that has no bearing on the matter, and is better suited to a thread about the nature of time.

I understand and appreciate your patience indulging my curiosity.

 

[river]

What is determined is based on a material Universe .

Energy , matter .

 

[Vociferous]

Sarkus:

Even though you claim to have kept up with the thread, you seem to have missed this.

Eternalism - the proposition that past and future are as equally real as the present. In General Relativity time is a dimension, as real as any dimension of space, where "there/then" is just as real as "here/now" and our perception of the "flow" of time is more of an illusion or artifact of our senses.

"Physics, particularly 20th century physics, does have one lesson to impart to the free will debate; a lesson about the relationship between time and determinism. Recall that we noticed that the fundamental theories we are familiar with, if they are deterministic at all, are time-symmetrically deterministic. That is, earlier states of the world can be seen as fixing all later states; but equally, later states can be seen as fixing all earlier states. We tend to focus only on the former relationship, but we are not led to do so by the theories themselves." - https://plato.stanford.edu/entries/determinism-causal/#DetHumAct​

Presentism - the proposition that the present is all that is real and that past and future do not exist. If the past is not real, there is only a present record and subjective seeming of a past consistent with the present. In that case, antecedent would simply be that choice is among the factors that "logically precedes" effect.

Growing block - the proposition that the past and present are real and the future is not. If past inexorably leads to the present which inexorably leads to the future, there would be no reason to believe the future, alone, did not exist, unless it was not "set" until a contribution from the present.​

 

[iceaura]

Recall that we noticed that the fundamental theories we are familiar with, if they are deterministic at all, are time-symmetrically deterministic. That is, earlier states of the world can be seen as fixing all later states; but equally, later states can be seen as fixing all earlier states.

Quantum theory (and chaos theory, etc) can be taken without theoretical conflict as specifying that events are determined by chance, implying that a probability is a mathematically mediated perception of a thing (the feed from a virtual sensory organ, like a potential energy term or similar perceiving of what our physical senses cannot) - thus separating determinism from predictability.

In that case, earlier states determine but do not uniquely fix later ones - rather, they constrain them (narrowing as the time of measurement approaches).
Later states do not fix earlier states unless there is only one possible earlier state for a given later one - that seems unlikely, regardless of the role of probability.

the proposition that the present is all that is real and that past and future do not exist.

On the one hand, it takes a certain minimum interval of time for most things to exist. So without a real past they don't. On the other hand, the notion that something exists if it doesn't exist at this time seems confusion bound. The best exit from this box seems to be a reconsideration of what exactly is meant by the "present".

 

[Sarkus]

Sarkus:

Even though you claim to have kept up with the thread, you seem to have missed this.

I didn't miss it. Since I had no intention of interrupting your discussion with Baldeee, I didn't post a reply to it at the time, and only posted anything here because you appealed to the wider readership of the thread to support a claim that I personally could not support.

But to now address what you posted:

Your quote regarding the time-symmetry of determinism is saying nothing new, and has been discussed since by Write4U, Halc, and myself. Since you have stated that all theories of time do not negate what determinism is, or its nature, I am unsure why you have linked it to Eternalism when it would equally apply to all the theories, right? This quote simply says that it has been noticed that the fundamental theories are time-reversible (as it has been referred to) - i.e. are deterministic should the arrow of time be reversed. This is not necessarily true of all deterministic systems, but the quote is effectively saying that it seems to be true of the laws of our universe. And that we tend to focus on the forward arrow of cause and effect, rather than appreciating that, in such a time-reversible system, the effect also fixes the cause.

But this applies to all of the theories of time. Not just eternalism, but to any theory of time that allows determinism. It is not, as you seem to be suggesting, a quote per se in support of Eternalism, but is simply a point to note about the nature of determinism and time-reversible systems.

If you are posting the quote in support of Eternalism, then you are in effect saying that the other theories do not support determinism.
So which is it?

As to your interpretations of the theories, I do not see how they in any way impact the question of the thread. Or at least you have yet to actually explain how. Your interpretation of Presentism, for example, introduces the notion of choice but does not explain it, and thus simply seems to (at least start to) beg the question. And your interpretation of the Growing block confuses what it means to exist with what it means for something to be fixed or certain.
As has been explained, determinism is the principle that the cause wholly determines the effect. And if the effect is wholly determined then it is certain, based on the cause. If the effect is certain, then in any system where that effect is the next cause, the subsequent effect is then certain. And all things in that direction of flow becomes certain. This is separate from the ontological matter of whether the future or past exist.

 

[Sarkus]

Quantum theory (and chaos theory, etc) can be taken without theoretical conflict as specifying that events are determined by chance, implying that a probability is a mathematically mediated perception of a thing (the feed from a virtual sensory organ, like a potential energy term or similar perceiving of what our physical senses cannot) - thus separating determinism from predictability.

Unfortunately you continue to misundersand what it means for something to be deterministic. You miss where it requires the effect to be wholly determined by the cause. While it is true that we can mathematically express the probability of the effect with respect to the cause, any probabilistic outcome is simply not wholly determined. To be wholly determined the cause must always lead to the same effect. Not 50% of the time to effect A and 50% of the time to effect B. In this example, there is something else, other than the cause stated, that is actually determining whether it is A or B. To summarise: being able to be expressed mathematically is not the same as it being deterministic.
Your lack of comprehension of what it means for a system to be deterministic really does cripple you in this thread. It has done from the outset.

Furthermore, chaos in a deterministic system is simply to do with the sensitivity of the end state of the system to the initial state.
"Chaos: When the present determines the future, but the approximate present does not approximately determine the future." - Edward Lorenz
Since we are unlikely to know the initial state of a complex chaotic system, we can at best estimate the outcome probabilistically - hence such things as weather forecasts.

In that case, earlier states determine but do not uniquely fix later ones - rather, they constrain them (narrowing as the time of measurement approaches).

Hence you're not actually describing a deterministic system. To quote the first line of wiki on the matter:
"In mathematics, computer science and physics, a deterministic system is a system in which no randomness is involved in the development of future states of the system.[1] A deterministic model will thus always produce the same output from a given starting condition or initial state.[2]"
(references can be linked to from wiki).
To summarise: if cause X inherently leads to A 50% of the time, and to B the other 50% of the time, then you are not looking at a deterministic system.

Later states do not fix earlier states unless there is only one possible earlier state for a given later one - that seems unlikely, regardless of the role of probability.

In time-reversible systems, that is, in systems that are deterministic in both normal and a reversed flow of time, later states do fix earlier states. Pretty much by definition.