I recently had an intriguing conversation on free will. Here are my thoughts.
If we had perfect information about what is going on in one's brain, I believe we can accurately predict one's actions. Our thoughts—it should be pointed out—are a series of electrical impulses taking place in our brains so, to predict one's actions, we must have perfect information regarding the electrons (both the position and momentum) in one's brain.
Note that while knowing the position of the electrons will give us information as to what is going on in one's mind at an instant in time, we must also know the momentum to accurately predict their actions as we must know where these electrons are going. But, Heisenberg's uncertainty principle makes this impossible as we can never know the precise position and momentum of an electron at the same time. So, this uncertainty leads me to believe that we do have some sort of free will, at least in the sense that it is impossible to predict one's actions.
However, I also believe that our thoughts and actions are constrained by the information we've gathered from our observations. After all, our thoughts are nothing more than the compilation or byproduct (inductive and deductive reasoning) of what we observe. Even creativity is nothing more than drawing connections between our thoughts. Put in the context of free will, the decisions we make come from the choices we have, and the choices we have are constrained by our thoughts which are obtained from outside sources. So, because our actions are constrained by what we observe, and we cannot perceive the choices that exist outside of this constraint, I am led to believe that we do not have free will.
To conclude, whether or not I believe in free will really boils down to how we define "free will". If we define "free will" as the inability to predict someone's actions, then I do believe in free will because of Heisenberg's uncertainty principle. On the other hand, if we define "free will" as having complete control over our actions, I do not believe in free will because of the choice constraint mentioned in the previous paragraph.