Indeed, what is free will ?
You have a choice and make a decision. But if you chose the more logical / easier / more beneficial option, then your "choice" was in fact predetermined by the logic you followed.
If you made a choice on the whim of your mood at the moment, it was still determined by your chemical and hormone balance you had at the moment, so it was again in a way predetermined, i.e. if one had the complete knowledge of your brain state, your choice could have been predicted.
Off:
Even if you flip a coin to make a decision, the actual force you flipped, the physical properties of the coin, the air movement etc. would allow for precise calculation and determination of the results -- thus it isn't random.
On
So, Free Will would have to be defined as something that a single person decides to do and is not restricted / prevented by other people to do so. So we have to ignore that the person's thinking itself is determined by his/her logic and/or brain chemistry.