I think that I understand how it is that we can know an electron's position but not its velocity and vice versa. I also understand that Einstein did not think that this affected determinism but that nowadays, most physicists do believe that uncertainty would cast doubt on a deterministic interpretation of the universe.

What I don't understand is how uncertainty would practically affect causality.

If cause and effect does nort apply everywhere, what can be there in its place? Is the uncertainty in my brain electrons analogous to my actually exercising free will? Surely no-one really believes this, do they? What then are the implications of the uncertainty principle for free will and consciousness?

[INDENT]The possible choices I have on my menu before me still exist and I will still choose of my own accord, I'm simply not aware of the near-infinite variables involved that will lead me to that decision. This doesn't mean I don't have a choice; Even if I could know all the variables that'll ultimately lead me to that decision, I'd still have a choice. Despite how it 'feels', these aren't mutually-exclusive.
[/INDENT]Here's my qualifier and what I think is the Key: We can't know all the variables involved in events, actions or decisions; there's simply too much to take into account - too much to weigh. As you mentioned with your electron-predictability point, there are some aspects of physics we simply can't predict. This does not invalidate the cause-and-effect principle at all, it simply says we haven't the means by which to exploit it to its logical permutation.

Does that make sense?

Uncertainty does not disrupt causality at all, you'll be pleased to know. The 'uncertainty' in a particle's position and velocity is a feature of a deterministically time-evolved wavefunction. I actually think its a bit of a misnomer, but it's a matter of interpretation. Some people interpret the wavefunction (or its square) at a given position as nothing more than the probability of finding the particle in each of those positions. I read it as any normal wave: that is, the particle is spread across all those positions at once. Thus the 'uncertainty' in position of a wave is nothing more than its spatial spread. Likewise the uncertainty in its momentum is nothing more than the dynamics of the wave components.

The breakdown in determinism lies in measurement, not propagation, since there is no known mechanism for time-evolving an 'uncertain' particle into a certain state (position, velocity, spin, energy, etc) that would explain observed statistical variation and no known time-interval over which this would happen if there were, though people are working on it. This is referred to as the 'instantaneous collapse of the wavefunction'.

As for free will and consciousness, this probabilistic collapse is unlikely to have any implications since the units of the body and brain, from atoms to cells to organs, are so large compared to their wavelengths that one observes no probabilistic behaviour (though it has been measured for a fairly large molecule, it is a very small effect that is manifest in very specific circumstances measured by very sensitive apparatus).

I agree with all you say. Most experts in QM are now willing to say that causality breaks down on the micro-level. The notion that the problem is merely epistemic is a view of more than a half-century ago.

I want only to add that the supposed problem about free will and micro-physics pertains only to what philosophers and theologians think of as the problem of free will having to do with determinism. But nothing whatsoever to do with what we ordinarily think of as free will which is just the absence of compulsion; not the absence of causation.

You're right - I don't think it would.

I'm no expert - to be sure - but what I'd say is this: I do have free will -and- you could predict my decisions beforehand were you to know all factors, all variables and their appropriate weights, my past, my feelings, emotions, physical state and more. To say that the cause and effect principle enables the possibility to predict future events doesn't preclude the concept of free will one iota.[INDENT]The possible choices I have on my menu before me still exist and I will still choose of my own accord, I'm simply not aware of the near-infinite variables involved that will lead me to that decision. This doesn't mean I don't have a choice; Even if I could know all the variables that'll ultimately lead me to that decision, I'd still have a choice. Despite how it 'feels', these aren't mutually-exclusive.
[/INDENT]Here's my qualifier and what I think is the Key: We can't know all the variables involved in events, actions or decisions; there's simply too much to take into account - too much to weigh. As you mentioned with your electron-predictability point, there are some aspects of physics we simply can't predict. This does not invalidate the cause-and-effect principle at all, it simply says we haven't the means by which to exploit it to its logical permutation.

Does that make sense?

Even if I could know all the variables that'll ultimately lead me to that decision, I'd still have a choice.

The breakdown in determinism lies in measurement, not propagation, since there is no known mechanism for time-evolving an 'uncertain' particle into a certain state (position, velocity, spin, energy, etc) that would explain observed statistical variation and no known time-interval over which this would happen if there were, though people are working on it. This is referred to as the 'instantaneous collapse of the wavefunction'.

Ummm no? If the variables lead you to the choice you have no choice or else the variables didn't lead you to that choice. If you still have a choice you can not have calculated the variables correctly.

Determinism implies that it is in principle possible to predict a given choice but surely that does not affect our free will. We do still have the choice. At worst, perhaps determinism means that we are not quite as capricious as we might otherwise be.

We do still have the choice.

I agree with all you say. Most experts in QM are now willing to say that causality breaks down on the micro-level. The notion that the problem is merely epistemic is a view of more than a half-century ago.

I want only to add that the supposed problem about free will and micro-physics pertains only to what philosophers and theologians think of as the problem of free will having to do with determinism. But nothing whatsoever to do with what we ordinarily think of as free will which is just the absence of compulsion; not the absence of causation.

Hi Kenneth,

This is something I have been thinking about recently, so it's great to find this discussion.

QM is just the latest theory, isn't it? Won't it be overturned completely in due course by a more powerful theory? And QM itself hasn't got to the bottom of things yet, has it? The original poster made reference to particles, Bones-O has shown us that there is still disagreement about wave/particle duality.

My own current thinking is that there are no particles, because the universe is fundamentally an indivisible whole. There are no individual objects, there are also no individual events, and therefore ultimately no causation, all these things are extremely useful fictions, partial descriptions of aspects of the universe as we experience them. If our experience was removed from the picture, the universe would be a very different thing, and we find it difficult to appreciate how different.

I'd be interested in your views, as well as those of Bones-O and the other contributors.

QM is just the latest theory, isn't it? Won't it be overturned completely in due course by a more powerful theory? And QM itself hasn't got to the bottom of things yet, has it? The original poster made reference to particles, Bones-O has shown us that there is still disagreement about wave/particle duality.

My own current thinking is that there are no particles, because the universe is fundamentally an indivisible whole. There are no individual objects, there are also no individual events, and therefore ultimately no causation, all these things are extremely useful fictions, partial descriptions of aspects of the universe as we experience them. If our experience was removed from the picture, the universe would be a very different thing, and we find it difficult to appreciate how different.

Yes, it is the latest theory. But I don't know that it is only the latest theory. It may be the correct theory. That other theories have been "overturned" does not show that QM will be overturned. We may not be certain it is true, but that doesn't mean that it isn't true, does it? In any case, the point is that indeterminacy is not epistemic, as far as we know. It is metaphysical. But there is no good reason to think it affects human actions and choices.

Well your view that there are no particles is not one held by most scientists, so I will have to go along with them. It is hard to see why the postulation of particles would be so useful unless it was true.

The history of science, Kuhn argued, is punctuated by violent intellectual revolutions that overturn long periods of conservative puzzle-solving. Periods of so-called "normal" science are characterised less by independent and objective research than by adherence to agreed assumptions and expected outcomes. During periods of normal science, anomalous or unexpected findings get brushed aside as either irrelevant or problems to be solved another time. Original research that questions the current assumptions of accepted theory are often debunked as wild and useless speculation. This gives rise to Kuhn's notion of a paradigm. The current paradigm is a a web of interwoven assumptions and beliefs shared by a particular community which underlies and sets the agenda for current research.

According to Kuhn, only results which tend to strengthen the normal paradigm get accepted during periods of normal science. The paradigm itself is never questioned or criticised. However, from time to time paradigms are overthrown by intellectual revolutions, when the paradigm fails to provide adequate models for observed phenomena, or a new, more powerful model has a greater explanatory force but requires a "paradigm-shift", a revolution takes place.

Overturned completely? How? Will we suddenly discover that microchips and CD players don't actually work? There is still a lot to figure out about QM, and there may be a better theory turning up that explains QM from a more fundamental level.

I think anyone who accepts QM has already accepted that the universe is very different to our experience of it.

I'm not sure, though, how those experiences would arise out of your indivisible universe theory. My experiences are not your experiences, and yet both exist in the universe. If the universe is indivisible, why do our experiences seem utterly separated?

Clocks didn't stop working when Einstein overturned Newton.

But you seem to be saying that QM says something about parts of the universe that you haven't experienced, maybe that you couldn't experience, however remotely. So that would mean, nothing we know about would stop working if that theory was overturned.

That isn't really what I am paying my scientists to do.

Let me know if that hasn't entirely transformed your understanding of the universe.

I think anyone who accepts QM has already accepted that the universe is very different to our experience of it.

I'm just saying that a lot of aspects of QM are counter-intuitive, that things we take for granted are often thwarted in QM.

Those seem to be two very different statements. How are things you take for granted thwarted by QM? How does the thwarting take place?

For examples: that empty space isn't empty (Casmir effect); or that two simultaneous events separated by great distances can be causally linked (EPR paradox); or that objects can be two things at once (Schrodinger's cat); or that processes can occur backwards in time (CPT symmetry); or that an object can get somewhere by more than one path (double slit experiment, path integral formalism); or that something can have spin but not be spinning; or that matter can be created or destroyed (pair creation/annihilation); or that energy isn't quite conserved (uncertainty principle).

Maybe we could just take one of your examples: would it be ok to take the first, and maybe you could tell me what you think is our experience of empty space, and how the Casimir effect shows that the universe is different to that experience?