The free will debate is often characterised as a debate about whether we can make decisions that are not simply mechanically determined. It asks whether our decisions are as inevitable as the movement of a car's wheels once the gear train is in motion or whether there is something more to human life than just one event pressing on another. However, although these questions are interesting the empirical approach shows that the problem of free will is far more serious.
Try taking a conscious decision right now. You may be sitting reading but sit back and try to decide to do something. When I sit back and take a "conscious" decision my eyes might focus on a finger or I might have some tension in my leg and then the thought "I will move this finger" or "I will move this leg" pops into mind. It is obvious that non-conscious parts of my body and brain are creating this conscious experience because it just pops into mind. This raises an interesting problem: do we ever have conscious decisions or do decisions just pop into mind?
There is a logical flaw in the concept of simple, conscious, free will because if you are to consciously decide to "will" something to happen this conscious decision cannot just pop into your mind. If it just popped into mind the decision itself would be non-conscious. To make a conscious decision you must consciously decide that you are going to consciously decide that you are going to consciously decide that..... and so on ad infinitum. The only alternative to this infinite regress is to accept that what we believe to be conscious decisions are usually just things that pop into mind - the decision occurs in our experience but we did not make the decision consciously .
Neuroscientists have demonstrated this non-conscious nature of "conscious" decision making by discovering that preparatory electrical activity in the brain can precede a "conscious" decision by 0.2 to 7 seconds (See Time and conscious experience). When a decision is taken the timing of mental and neural events is such that the neural events precede conscious experience by substantial amounts of time*. The measurements of brain activity confirm the obvious logical point that you cannot know you have made a decision until you have made it!
This means that the only form of "conscious" decision that is feasible is like "biofeedback" in which the conscious state evoked by an event either enhances or depresses the future likelihood of the event. Conscious experience would then allow the acquisition of skills by providing feedback after each trial. Similarly, by rehearsing events mentally it might be possible to test the effects of events on conscious experience and amend future, non-conscious processing appropriately. This would also allow us to rehearse decisions before actually applying them to the world, it would allow us to think "suppose I moved my finger, what would that be like?" without actually moving the finger. Notice that I am not talking about a rehearsal in the non-conscious parts of my brain, I am asking whether introducing a rehearsal into my conscious mind can affect the outcome of the rehearsal in ways that might not occur for non-conscious rehearsals.
In the light of this analysis the proposal might be made that we could have "conscious" decisions if a conscious state can modulate the likelihood of particular actions.
Can the state of my mind affect the non-conscious parts of my brain? Well, the fact that I can write about the form of my conscious experience shows that this is possible: if the state of my mind, called "my conscious experience", can be described then there must be a physical link from this state to the written word via the non-conscious parts of the brain that control writing. Of course, the non-conscious parts of my brain have loaded my conscious experience with most of its data content so the only unknown component of my experience, as far as the non-conscious part of my brain is concerned, is the form of this experience (its multidimensional geometric layout). The most important aspect of this form is the continuity of the content over time. A simple signal that indicates that an image or sound that has popped into my conscious experience is consistent or inconsistent with a sound or image that is already in my experience might be sufficient to provide the required communication of this continuity. The exact mechanism for such a signal is obscure but it might be speculated that interference could occur at the point in the present instant where the vectors that constitute experience are directed.
If conscious experience is able to influence my decisions by training the non-conscious parts of my brain then why would I want to train myself to have a particular conscious state? Am I able to meditate and bring the non-conscious parts of my brain around to the conclusion that a particular state of my conscious mind is preferable? If this is indeed possible then I may have a conscious will that is free because, as is discussed in time and conscious experience, the selection of a mental state may involve a selection of a particular quantum state of my brain. The selection of a particular quantum state is a non-deterministic process and my will would be free, albeit delayed and not too good for rapid decision taking.
See http://www.blutner.de/philom/consc/consc.html for an interesting review of Libet's experiments.
* It is possible to train subjects to respond to flashing lights by pressing a button or by blinking to such an extent that this action becomes a reflex. Subjects who respond to events in a reflex fashion should, in principle, be able to deliver a response before they would report that they have made any decision to respond. This, along with the fact that you can only know you have made a decision once you have made it means that experiments on "conscious" decisions should be able to show the following conditions. Firstly brain activity must always precede the notification that a conscious decision has been made, secondly it should be possible to withhold an action so that the "conscious" decision always precedes the action and thirdly it should be possible to train reflexes so that some actions definitely precede their associated "conscious" decisions. The various experiments on the neuroscience of decision taking have confirmed all of these conditions.