# How physicists handle the idea of Free Will?

1. Feb 9, 2012

### fbs7

I have always been quite curious how physicists reconcile the concept free will with the determinism of physics.

By determinism I mean the one at macroscopic level, because I know that at quantum level most of the things are based on probabilities. So there's no free will for an electron.

But, at macroscopic level, everything seems to have some equation that determines its future, even if that's chaotic and very difficult (for us) to predict. So there's no free will for the Moon, as we'll know its exact position million of years in the future; in the same way, there's no free will for a drop of water falling in a waterfall - it's future is pre-determined, even if it is very difficult for us to calculate that.

Similarly, there's no free will for a computer, given for the same set of inputs it will always produce the same outputs.

So if I'm to believe in physics determinism, I should give up on the concept of free will, because like a computer whatever choice I'm going to make has been pre-determined by my history, genetics, inputs, environment and so forth - even if that choice may be, to our current capabilities, unpredictable, because it would depend on a very complicated equation.

That is very depressing, and as I love physics and much as I love my free will, I just don't think about that. So how do physicists answer that dilemma - is there free will in physics?

2. Feb 9, 2012

### Staff: Mentor

What do you mean by 'free will'?

3. Feb 9, 2012

### fbs7

That's a good question, and I bet every person will have a different answer. I think this one from Merriam-Webster reflects my thinking:

free will (noun)
1. ..
2. freedom of humans to make choices that are not determined by prior causes or by divine intervention

4. Feb 9, 2012

### Staff: Mentor

Can you give an example of making a choice not determined by prior causes. Not sure what that would mean.

5. Feb 9, 2012

### fbs7

I reckon you don't believe in free will.

That's a perfectly good point of view - nothing wrong in that. I understand you don't need to reconcile that with physics determinism.

6. Feb 9, 2012

### Staff: Mentor

Still waiting for an example so I can understand what you mean by the term.

7. Feb 9, 2012

### fbs7

The way I see it, free will is when Joan d'Arc chose to be burned instead of saving herself by reneging her beliefs. The way I see it, it was her choice.

8. Feb 9, 2012

### Ryan_m_b

Staff Emeritus
Is it possible to choose what you believe? Clearly her beliefs were strong enough so that when she weighed up the possible options to her burning to death was more desirable than condoning her beliefs.

The point being here that when you "make a choice" you unconsciously and consciously weigh up the ramifications of the options. How you judge the options is based on your accumulated life experience which was largely/entirely out of your control. So imagine that Alice is observed her entire life by Bob and that Bob has a team of expert psychologists. If Bob observes Alice presented with a choice he and his team could use the data and knowledge they have to build a predictive model and predict how Alice will make her decision because what she chooses will be based on her judgement which is built from past experience.

9. Feb 9, 2012

### chingel

Are you sure her actions weren't determined by her past and brain wiring?

10. Feb 9, 2012

### fbs7

So if I write "ABC", then before you read my post it's already pre-determined that you're going to answer "DEF", based on your past experiences, brain wiring, environment, history, etc...?

That is, no quantum processes can modify that, no still-undiscovered factors can influence it, there's nothing else besides working just like a computer - known outputs for known inputs?

11. Feb 9, 2012

### Ryan_m_b

Staff Emeritus
Yes I don't see why not. My entire personality is a combination of how my biology reacts with my environment over time, what I know and what I can do is also a product of this. Put the two together and no matter what I do there is a reason that has its basis in some past event.
Even if we propose there was some sort of quantum randomness how does that bring back "free will"? If anything that's less free. With regards to the rest yes, the physical brain and it's physical mechanical processes are not only all that we have found they are all that is indicated.

(Also just some advice but you might want to consider asking for the title of this thread to be modified to "How scientists..." and moved to the biology forum. Physics isn't really the discipline you want to study if you are looking into cognition and behaviour)

Last edited: Feb 9, 2012
12. Feb 9, 2012

### ModusPwnd

I think in the context of this question free will is best described as downward causation.

13. Feb 9, 2012

### Staff: Mentor

What does that mean?

14. Feb 9, 2012

### ModusPwnd

Simply that the question of free will from a physics perspective is essentially (IMO) a question about downward causation. Rejecting the possibility of downward causation is rejecting free will and finding a case of downward causation tentatively leaves free will on the table.

15. Feb 9, 2012

### Ryan_m_b

Staff Emeritus
And what exactly is "downward causation" and how does it factor into this specifically?

16. Feb 9, 2012

### Staff: Mentor

What do you mean by 'downward causation'?

17. Feb 9, 2012

### ModusPwnd

Oh, sorry. Downward causation is simply cause and effect working from 'top' level complex processes down to the fundamental 'low' level processes. Physicists generally work under the assumption of reductionism which has been (somewhat) fruitful but at the moment universal reductionism is just an assumption. There is no evidence that all complex phenomenon can be reduced to the physics of the basic constituents (though that is our working hypothesis).

Note that I am not supporting the idea of downward causation in this thread, I am simply casting the notion of Free Will as an issue of downward causation.

Last edited by a moderator: May 5, 2017
18. Feb 9, 2012

### Ryan_m_b

Staff Emeritus
The link you provided has no mention of free will. How specifically do you think that downward causation means that free will is left on the table? I'm sorry if I've missed something but so far all I've seen is your assertion that downward causation could preserve free will (whatever that means) with no evidence to back it up.

19. Feb 9, 2012

### ModusPwnd

If the actions we make are a function of the micro state, then there can be no free will. Will emerges as a macroscopic phenomenon. If that macroscopic phenomenon is completely a function of the micostate, then any action of that will is not free. But if that macroscopic state is capable of exercising a downward cause and effect then that will is free. That is, the macrostate is the cause rather than the effect.

20. Feb 9, 2012

### Ryan_m_b

Staff Emeritus
Why is that different from from any form of mechanical feedback? And why can an event be both a cause and an effect?