Quantum indeterminacy is irrelevant because at macroscopic levels all the quantum weirdness (e.g. quantum indeterminacy and superposition) averages out.
— Truth Seeker
Only sometimes, but not the important times. There are chaotic systems like the weather. One tiny quantum event can (will) cascade into completely different weather in a couple months, (popularly known as the butterfly effect) so the history of the world and human decisions is significantly due to these quantum fluctuations. In other words, given a non-derministic interpretation of quantum mechanics, a person's decision is anything but inevitable from a given prior state. There's a significant list of non-deterministic interpretations. Are you so sure (without evidence) that they're all wrong?

Anyway, it's still pretty irrelevant since that sort of indeterminism doesn't yield free will. Making truly random decisions is not a way to make better decisions, which is why mental processes do not leverage that tool. — noAxioms

Thank you for the thoughtful response. You raise a key point — that in chaotic systems, even minute quantum fluctuations could, in theory, scale up to macroscopic differences (the “quantum butterfly effect”). However, I think this doesn’t meaningfully undermine determinism for the following reasons:

1. Determinism vs. Predictability:
Determinism doesn’t require predictability. A system can be deterministic and yet practically unpredictable due to sensitivity to initial conditions. Chaos theory actually presupposes determinism - small differences in starting conditions lead to vastly different outcomes because the system follows deterministic laws. If the system were non-deterministic, the equations of chaos wouldn’t even apply.

2. Quantum Amplification Is Not Evidence of Freedom:
As you already noted, even if quantum indeterminacy occasionally affects macroscopic events, randomness is not freedom. A decision influenced by quantum noise is not a “free” decision — it’s just probabilistic. It replaces deterministic necessity with stochastic chance. That doesn’t rescue libertarian free will; it only introduces randomness into causation.

3. Quantum Interpretations and Evidence:
You’re right that there are non-deterministic interpretations of quantum mechanics - such as Copenhagen, GRW, or QBism - but there are also deterministic ones: de Broglie-Bohm (pilot-wave), Many-Worlds, and superdeterministic models. None of them are empirically distinguishable so far. Until we have direct evidence for objective indeterminacy, determinism remains a coherent and arguably simpler hypothesis (per Occam’s razor).

4. Macroscopic Decoherence:
Decoherence ensures that quantum superpositions in the brain or weather systems effectively collapse into stable classical states extremely quickly. Whatever quantum noise exists gets averaged out before it can influence neural computation in any meaningful way - except in speculative scenarios, which remain unproven.

So, while I agree that quantum indeterminacy might introduce genuine randomness into physical systems, I don’t see how that transforms causality into freedom or invalidates the deterministic model of the universe as a whole. At best, it replaces determinism with a mix of determinism + randomness - neither of which grants us metaphysical “free will.”

I don't know enough about it to have an opinion about it. Please tell me more about how quantum events affect the weather. Is there a book you can recommend so I can learn more about this? Thank you. — Truth Seeker

Apologies for not seeing that question for months.

There are whole books, yes. A nice (but still pop) article is this one:
https://www.space.com/chaos-theory-explainer-unpredictable-systems.html
The wiki version: https://en.wikipedia.org/wiki/Butterfly_effect
The latter link in places talks specifically about the small initial differences being different quantum outcomes. The best known quantum amplifier is Schrodinger's cat, where a single quantum event quickly determines the fate of the cat, even if it isn't hidden in a box.

1. Determinism vs. Predictability:
Determinism doesn’t require predictability. A system can be deterministic and yet practically unpredictable due to sensitivity to initial conditions. — Truth Seeker

Even classical mechanics has been shown to be nondeterministic. Norton's dome is a great example of an effect without a cause. Nevertheless, a deterministic interpretation of physics would probably require hidden variables that determine the effect that appears uncaused.

Chaos theory actually presupposes determinism - small differences in starting conditions lead to vastly different outcomes because the system follows deterministic laws.

But it doesn't require determinism. Chaos theory applies just as well to nondeterministic interpretations of physics.

If the system were non-deterministic, the equations of chaos wouldn’t even apply.

Well, deterministic equations would not apply. How about Schrodinger's equation? That function is very chaotic, and it is deterministic only under interpretations. like MWI.

2. Quantum Amplification Is Not Evidence of Freedom:
As you already noted, even if quantum indeterminacy occasionally affects macroscopic events, randomness is not freedom. A decision influenced by quantum noise is not a “free” decision — it’s just probabilistic. It replaces deterministic necessity with stochastic chance. That doesn’t rescue libertarian free will; it only introduces randomness into causation.

Agree. So very few seem to realize this.

To me, freedom is making your own choices and not having something else do it for you. Determinism is a great tool for this, which is why almost all decision making devices utilize as much as possible deterministic mechanisms such as binary logic.

3. Quantum Interpretations and Evidence:
You’re right that there are non-deterministic interpretations of quantum mechanics - such as Copenhagen, GRW, or QBism - but there are also deterministic ones: de Broglie-Bohm (pilot-wave), Many-Worlds, and superdeterministic models.

Superdeterminism is not listed as a valid interpretation of QM since it invalidates pretty much all empirical evidence. It's a bit like BiV view in that manner. The view doesn't allow one to trust any evidence.

MWI is a good example of chaotic behavior. You have all these worlds, and since weather and which creatures evolve are all chaotic functions, most of those worlds don't have you in it, or even humans. Most of those worlds don't have Earth in it. The deterministic part only says that all these possibilities must exist. There's no chance to any of them. But do they exist equally? That's a weird question to ponder.
No, I don't buy into MWI since I feel it gets some critical things wrong.

None of them are empirically distinguishable so far. Until we have direct evidence for objective indeterminacy, determinism remains a coherent and arguably simpler hypothesis (per Occam’s razor).

Of the two deterministic interpretations you mention, MWI is arguably the simplest, and DBB is probably the most complicated. This illustrates that 'deterministic' is not necessarily 'simpler'.

4. Macroscopic Decoherence:
Decoherence ensures that quantum superpositions in the brain or weather systems effectively collapse into stable classical states extremely quickly.

At least under interpretations that support collapse.

Whatever quantum noise exists gets averaged out before it can influence neural computation in any meaningful way

Yes, that what I meant by 'utilize as much as possible deterministic mechanisms'.

except in speculative scenarios, which remain unproven.

In particular, no biological quantum amplifier has been found, and such a mechanism would very much have quickly evolved if there was any useful information in that quantum noise.

Bottom line is that we pretty much agree with each other.

Thank you very much for the fascinating links you posted. I really appreciate your thoughtful follow-up. I agree that we’re largely converging on the same view.

Regarding Norton’s dome, I think it’s an interesting mathematical curiosity rather than a physically realistic case of indeterminism. It depends on idealized assumptions (e.g., perfectly frictionless surface, infinite precision in initial conditions) that don’t occur in nature. Still, it’s a useful illustration that even Newtonian mechanics can be formulated to allow indeterminate solutions under certain boundary conditions.

As for the quantum–chaos connection, yes - Schrödinger’s cat is indeed the archetypal quantum amplifier, though it’s an artificial setup. In natural systems like weather, decoherence tends to suppress quantum-level randomness before it can scale up meaningfully. Lorenz’s “butterfly effect” remains classical chaos: deterministic, yet unpredictable in practice because initial conditions can never be measured with infinite precision. Whether a microscopic quantum fluctuation could actually alter a macroscopic weather pattern remains an open question - interesting but speculative.

I agree with you that determinism is a great tool for agency. Even if all our choices are determined, they are still our choices - the outputs of our own brains, reasoning, and values. Indeterminacy doesn’t enhance freedom; it merely adds noise.

On superdeterminism: I share your concern. It’s unfalsifiable if taken literally (since it could “explain away” any experimental result), but it remains conceptually valuable in exploring whether quantum correlations might arise from deeper causal connections. I don’t endorse it, but I don’t dismiss it either until we have decisive evidence.

You put it well: the bottom line is that we mostly agree - especially that neither pure determinism nor indeterminism rescues libertarian free will. What matters is understanding the causal web as fully as possible.

Thanks again for such a stimulating exchange. Discussions like this remind me how philosophy and physics intersect in fascinating ways.

Kind of catching up on posts made since the 8 month dormancy.

Are we free agents or are our choices determined by variables such as genes, environments, nutrients, and experiences? — Truth Seeker

Depending on definitions, the two are not necessarily exclusive.

Not for me. I feel many choices as I'm making them. I struggle with them, looking for a reason too give one option a leg up. — Patterner

There you go. You seem to have a grasp on what choice actually is.

Technically, no, because the choice was made and we're not able to ever review it in this way. — AmadeusD

Being able to review it amounts to different initial conditions.

Theoretically, I think yes. But this involves agreeing that something billions of years ago would have to have happened differently.

Billions of years?? It would be interesting, in say MWI, so see how long it take for two worlds split from the same initial conditions to result in a different decision being made. It can be one second, but probably minutes. Maybe even days for a big decision like 'should I propose marriage to this girl?'. But billions of years? No. Your very existence, let along some decision you make, is due to quantum events at most a short time before your conception.

If hard determinism is true, then all choices are inevitable — Truth Seeker

Any determinism. That is also true under what is called soft determinism.
But as you've posted, determinism has little if anything to do with free will, or with moral responsibility. Substance dualism is a weird wrench in this debate. If there are two things, only the one in control is responsible for the actions of the body. So say if I get possessed by a demon (rabies say) and bite somebody, infecting them, am I responsible for that or is the demon? Is it fair to convict a rabid human of assault if they bite somebody? Kind of a moot point since they're going to die shortly anyway.

But I come at this from the opposite direction, it is the constraints of the hard physical world which restrict my strong free will. — Punshhh

Sure. I will to fly like superman, but damn that gravity compelling otherwise.

Take that away and I would have near absolute freedom.

Take away that and there would be no you have this freedom.

Assume the mind is not equivalent to the brain. Could you have chosen differently? You still had a set of background beliefs, a set of conditioned responses, a particular emotional state and physical state, were subject to a particular set of stimuli in your immediate environment, and you had a particular series of thoughts that concluded with the specific ice cream order that you made. Given this full context, how could you have made a different choice? — Relativist

Yes. This is why determinism is irrelevant to the free will debate.
If a supernatural entity is making your choices, then not only is determinism false, but all of natural physics is false. A whole new theory is needed, and there currently isn't one proposed.

As has been pointed out, natural physics is regularly updated, and thus the current consensus view is not 'the truth'. But despite all the updates and new discoveries, one thing stands: Physics operates under a set of rules. We're still discovering those rules, but some definitions of moral responsibility require the lack of any rules. That's not ever going to be found to be the case.

Because you're ignoring another major factor in Human Decision Making, namely randomness. — LuckyR

I pretty much deny this. All evolved decision making structures have seemed to favor deterministic primitives (such as logic gates), with no randomness, which Truth Seeker above correctly classifies as noise, something to be filtered out, not to be leveraged.

Sure, unpredictable is sometimes an advantage. Witness the erratic flight path of a moth, making it harder to catch in flight. But it uses deterministic mechanisms to achieve that unpredictability, not leveraging random processes.

Regarding Norton’s dome, I think it’s an interesting mathematical curiosity rather than a physically realistic case of indeterminism. — Truth Seeker

Classical physics is a mathematical model, which some have proposed is reversible. No physics is violated by watching the pool balls move back into the triangle with all the energy/momentum transferred to the cue ball stopped by the cue.
Norton's dome demonstrates that classical mathematics is actually not reversible, nor is it deterministic, the way that the equations seem to be at first glance.

As for the quantum–chaos connection, yes
...
In natural systems like weather, decoherence tends to suppress quantum-level randomness before it can scale up meaningfully.

You have a reference for this assertion, because I don't buy it at all. Most quantum randomness gets averaged out, sure, but each causes a completely different state of a given system, even if it's only a different location and velocity of each and every liquid molecule.

Evolution depends on quantum randomness, without which mutations would rarely occur and progress would proceed at a snails pace. There's a fine balance to be had there. Too much quantum radiation and DNA gets destroyed before it can be filtered for fitness. Too little and there's no diversity to evolve something better.

Thank you for asking for a source. You’re right that quantum effects can, in principle, influence macroscopic systems, but the consensus in physics is that quantum coherence decays extremely rapidly in warm, complex environments like the atmosphere, which prevents quantum indeterminacy from meaningfully propagating to the classical scale except through special, engineered amplifiers (like photomultipliers or Geiger counters).

Here are some references that support this:

1. Wojciech Zurek (2003). Decoherence, einselection, and the quantum origins of the classical. Reviews of Modern Physics, 75, 715–775.
Zurek explains that decoherence times for macroscopic systems at room temperature are extraordinarily short (on the order of (10^-20) seconds), meaning superpositions collapse into classical mixtures almost instantly.
DOI: 10.1103/RevModPhys.75.715

2. Joos & Zeh (1985). The emergence of classical properties through interaction with the environment. Zeitschrift für Physik B Condensed Matter, 59, 223–243.
They calculate that even a dust grain in air decoheres in about (10^-31) seconds due to collisions with air molecules and photons - long before any macroscopic process could amplify quantum noise.

3. Max Tegmark (2000). Importance of quantum decoherence in brain processes. Physical Review E, 61, 4194–4206.
Tegmark estimated decoherence times in the brain at (10^-13) to (10^-20) seconds, concluding that biological systems are effectively classical. The same reasoning applies (even more strongly) to meteorological systems, where temperature and particle interactions are vastly higher.

In short, quantum coherence does not persist long enough in atmospheric systems to influence large-scale weather patterns. While every individual molecular collision is, in a sense, quantum, the statistical ensemble of billions of interactions behaves deterministically according to classical thermodynamics. That’s why classical models like Navier–Stokes work so well for weather prediction (up to chaotic limits of measurement precision), without needing to invoke quantum probability.

That said, I fully agree with you that quantum randomness is crucial to mutation-level processes in biology - those occur in small, shielded molecular systems, where quantum tunnelling or base-pairing transitions can indeed introduce randomness before decoherence sets in. The key distinction is scale and isolation: quantum effects matter in micro-environments, but decoherence washes them out in large, warm, chaotic systems like the atmosphere.

Here are two images I created to help explain my worldview: