# How can determinism and quantum mechanics coexist?



## URwhatUthinK (Feb 13, 2012)

So I've been on the 'no free will' train for a while now and actually started to read up and look into it more. Just recently read a very short read by Sam Harris called Free Will. He's a neuroscientist so he touches on how the brain works and isn't conscious at the point thoughts take hold. Although, it really isn't necessary to invoke any neuroscience to realize there is no free will. Harris believes the scientific community will eventually have to claim that free will is an illusion. Here is a video of him discussing for those interested (and there are longer ones on YT):






But onto the point.

So, I don't know much about quantum mechanics but we did touch on it in a philosophy of science class I had in the winter. The information isn't fresh in my mind...and I believe QM is basically the fringe of physical science so not much is known. But from what I remember QM basically says that at any time you are not observing the universe all particles and atoms exist in one super position of every possibility that they _could_ exist. And the current philosophical theories for QM suggest the possibility that basically any time we observe particles interacting with the universe, another universe is born and so on and so on...like one big tree with an incredibly large number of branches. So this would then suggest that there is a possibility of free will and that there are multiple versions of ourselves currently living in parallel universes in which he had made another choice.

But determinism would undermine this philosophy because determinism basically suggests that our environment, whether it's the external world or our brain chemistry, wills us to act. And we can't take credit for our actions because everything that has led up to the present point is influenced by a long series of causes that one could say was initially generated as soon as you developed consciousness in your mother's womb. This means there is a way in which everyone _must_ be and that we could never exist in a parallel universe...


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## sarek (May 20, 2010)

I think I can explain this. If you simplify QM as rolling the dice and observing whether or not the cat walks out of the box you can imagine that there are an incredibly large number of states the universe could be in the next moment.

We can only know what happened after it has happened. We can not make a 100% determination in advance. 

If you look back in time you see what has happened. That sequence could have happened any other way. In fact, the many world hypothesis says that all those other possible pasts actually DID happen and are still somewhere 'out there'

Now what if someone or something were to cherry pick any one of those timelines to live in. Would we ever have any way of knowing such cherry picking has happened? After all, it is still one of the many possible outcomes, just as valid as any of the others. 
I don't think we CAN know as long as we are stuck in our own one dimensional timescape. 

The universe as we see it is IMHO cleverly constructed to make it categorically impossible for us to determine whether or not there is free will.


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## URwhatUthinK (Feb 13, 2012)

Ah, okay that makes sense cuz it would be just how you can observe free will and feel as though there was a choice that could be made between A and B but of course there is always just one outcome and one choice. 

If the many worlds hypothesis is correct then that would mean there must be some sort of random element to the universe that takes place in some obscure way that could make these events possible to unfold in that many ways, right?


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## sarek (May 20, 2010)

The random element is QM. Or rather the fundamental inherent impossibility to make precise measurements at the quantum level, as determined by the uncertainly laws of Heisenberg. 

To be more precise, that law implies for instance(there are other 'pairs') that it is not possible to measure both velocity vector and position together with 100% precision. 
You can precisely pinpoint one or the other but not both 100% at the same time. The minimum total uncertainty is given by a formula containing Plancks constant which is very small but not zero.


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## Trinidad (Apr 16, 2010)

Post retracted for unneeded bitchiness. Carry on.


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## sarek (May 20, 2010)

EDIT: QM supersedes classical physics at the quantum level by introducing this indeterminability. Several outcomes are possible given each initial state. 
Conventional QM interpretations say that all outcomes that do not materialise are simply discarded. Many worlds says that they are not discarded but that they all become reality somewhere else in the timescape. Just not in our own 1 dimensional timeline.


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## TheProcrastinatingMaster (Jun 4, 2012)

That was really interesting and honestly I hadn't thought about free will in that sense. That said I can't help but rail against the idea that I lack free will.


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## wuliheron (Sep 5, 2011)

This is old muddled thinking on the subject and he has to be one of the worst lecturers I've heard.

The principle of Indeterminacy at the heart of quantum mechanics means we just don't know. That's what indeterminate means, you don't know. After a century of the greatest minds spending trillions of dollars to try and get some kind of hint of an underlying explanation for Indeterminacy the bottom line is still we-don't-know. All the hand waving, blue smoke, and mirrors in the world can't get around that simple fact nobody knows and it's perfectly OK to admit we are ignorant. There's even a new attempt being made now to see if causality itself is subject to Indeterminism.

Determinism and free will in the metaphysical sense then might forever remain mysteries. One possible way this might come about is if quantum effects are discovered in the brain itself. That might sound like a stretch, but physicists have already found quantum effects in photosynthesis and some types of animal navigation. Whatever the case might be it still doesn't change the fact that from our point of view determinism does appear to exist whether it's an illusion or not. As a pragmatist myself it makes no difference whatsoever on a day to day basis. Questions like whether the moon is still there when no one is looking just don't make the slightest difference in how I live my life.


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