When it comes to predicting human behavior, though, we stumble on severe epistemic roadblocks. Enter Vlatko Vedral, posing a physicist's counterpoint to Patricia Churchland's neurophilosophical musings. Are we free? Vedral concludes[sub req]:
To have the kind of free will we would like involves walking a fine line between determinism and randomness. We must be able to freely make our actions, but they should then result in deterministic (that is, non-random) effects. For example, we may want to be free to send our kids to a school of our choice. But then we also want to believe that the laws of physics (and biology, sociology and so on) ensure that going to a good school is highly likely to lead to a better life. Having free will is pointless without a certain degree of determinism.I disagree with Vedral's psychology of choice: we don't have to be sure that our actions will bring happy results, but just confident that our chances are good.
The same can be said about studying physics. I want to believe that the choice regarding which aspect of nature I want to study - whether I want to measure the position or velocity of a particle, for example - lies with me. But what I also want is some degree of deterministic behaviour in nature that would then permit me to infer laws of physics from any measurement that I choose to make. In fact, the only means we have for deducing the basic equations of quantum mechanics means that they are fully deterministic, just like those of Newtonian mechanics.
There is nothing mysterious or controversial about this, but look what happens when we apply this to ourselves. If we are all made up of atoms, and if atoms behave deterministically, then we too must be fully determined. We simply must share the same fate as the rest of the universe. When we look inside our brains, all we find are interconnected neurons, whose behaviour in turn is governed by their underlying molecular structure, which in turn is fully governed by the strict laws of quantum mechanics. Taking the argument to extremes, the laws of quantum mechanics ultimately determine how I deduce the laws of quantum mechanics, which appears to be a fully circular argument and therefore logically difficult to sustain....
The most honest position for a scientist on the question of free will is definitely agnostic: I simply do not know. What I do know is that when I was asked to write about free will as a physicist I found the idea so exciting that I had no choice but to agree to take it on.