Free will and quantum theory

Since Quantum Theory can predict precise events (even though probability is supposed to enter into the calculations) does this mean the universe is deterministic and there is no ‘free will’? Some contend that the probabilities involved in Quantum calculations means there is therefore no ‘strict causality’. But do not Quantum’s precise predictions imply ‘strict causality’? Strict causality implies an unalterable chain of events flowing from causes and therefore the future is ‘cast in stone’ and our brain’s calculations have been predetermined since forever.

The issue of QM and free will was discussed at length in this thread recently, for example.

There we end up getting into some pretty heady discussions about QM and free well.

The lack of future predictability does not automatically equate to free will. Personally I believe things are unpredictable but that free will may well be an illusion.

That’s my take on it as well. I’m not even sure how this “free will” thing is supposed to work anyway. Free from what? It is even possible to “choose” to “will” something?

Not being a quantum mechanic expert, I have a question - isn’t one of the fundamental principles of quantum mechanics that you can never precisely know the location and velocity of a particle? And would that therefore mean that that very uncertainty means one cannot ever predict things exactly, and can merely assign a probability of different outcomes? And further, would that not therefore mean free will does exist, because that quantum uncertainty is fundamentally unpredictable - one cannot know exactly what is happening in the brain at a given point, and thus cannot predict its course? And that is course is not entirely deterministic, but includes an element of randomness?

Physicists feel free to tell me I’m utterly off-base here. That’s just what I got from reading popular science books.

There is a big gap between non-determinism and free will.

I don’t think so. Let’s say a particular decision I make is driven by “flipping a coin” (exactly 50% chance either way) in some quantum way in my brain; which implies that I myself cannot know the outcome until I’ve already made the decision. How does that make that decision any more or less “free” than if there was some way of knowing beforehand with 100% certainty what I was going to decide?

Quantum mehcanics has two types of time evolution:

  1. the deterministic unitary evolution of the wavefunction described the Schrodinger equation (or another suitable wave equation). By ‘deterministic’ I mean that knowing the state of a quantum system undergoing unitary evolution at any time will uniquely determine it at any other time.

  2. the stochastic (i.e. probalistic) projection of the wavefunction on to an eigenvector known as “wavefunction collapse”.

Not sure I see anything against or for free will there.

I think free will is a bit sticky in general. if we examine 3 alternatives:

  1. Everything is predetermined. If everything is predetermined how can we have freewill as our choices are also predetermined an not choices as such as there exist no alternatives.

  2. The world is probabilstic at a fundamental level. Is having your life decided by the ‘flip of a coin’ really free will.

  3. The universe is fundamentally unpredictable and even assigning probabilties at a fundamental level is fraught with difficulties. Perhaps some might object to this as a bit airy-fairy as determinstic and stochastic systems pretty much cover every type of system we can conceive. If we cannot even reliably know the consequences or likely consequences of our actions at a fundamentallevel, do we have free will?

Not that

There’s always compatiblism, which argues that free will and determinism are compatible. The type of commpatiblism I find compelling would argue that the quoted statement is wrong.

Isn’t this always the case? If you know the outcome of a decision, then you’ve already made the decision. Knowing the outcome of your decision is the same as having already made a decision.

It’s the Schrodinger’s cat of decision making. Your decision is both right and wrong until you act upon it and know the result.