Erasmus, I've always had trouble understanding this experiment. Is it a necessary conclusion that the free will is nonexistant because scientists can see a process in the brain occurring before you push the button? Is it a viable solution to suggest that perhaps what scientists are seeing is simply the primary process that goes into an action? In your example, could it be that scientists could measure a certain chemical/electrical activity in the brain right before the action occurred and be led to conclude that this activity they measured was the internal decision being made to push the button?
The experiment is indeed a little bit fishy. Many other researchers have raised objections to the method and I cannot say that I am fully confident that the experiment reveals what Libet says it reveals.
But that aside, let's go back to what we really mean when we talk about free will. Obviously if everything is predetermined then we would probably come to the conclusion that we don't have free will. If on the other hand
everything is fundamentally random, then I suggest we don't have free will either. To me, the statement "I have free will" means "My conscious intention to act is the first and uncaused cause of at least some of my actions."
Imagine we had a device for mapping all functions of the brain
including consciousness, and a few milliseconds before somebody waves their right hand a light flashes under "conscious intention to wave right hand". Furthermore imagine that there is no prior neural cause of that conscious intention (suppose we can tell that too). To me this would be proof of free will. I would in fact define the will as the set of those uncaused mental causes.
On the other hand, imagine that, a few milliseconds before the "conscious intention to wave right hand" light flashes, a light someplace else in the neural mapper -- someplace
outside the "conscious event" area -- flashes, and that this relationship is observed every time somebody waves his hand. Since this neural event is part of the large-scale basically-deterministic brain, it must have a well-determined cause, which also must have a well-determined cause, etc, forming a chain that could be traced back more than just a few milliseconds. With enough obvservations, the neural mapper could be used to tell us days in advance that somebody was going to wave their hand -- no free will there. In other words, an unconscious causal chain leading up to a conscious event does not constitute free will.
To summarize, IMHO, if there are uncaused mental causes, we can call that free will. If there are no uncaused mental causes, we don't have free will. To me, Libet's experiment is (supposed to be interpreted as) evidence against the existence of uncaused mental causes.
That's the way I look at it.