News flash: there is no such thing as free will. I notice that this fact really irritates a lot of the reviewers here, which makes a good deal of sense. If we accept that there is no free will, we feel our own glory diminished, much as some feel when contemplating the idea that there is no afterlife. A lot of the arguments in favor of free will start with unfounded assumptions that there "must be" some form of free will, because that is the only possible explanation for order in the Universe. Order is really just a manifestation of the laws of physics, and doesn't need intelligent intervention, thank you. When a drop of water freezes into an exquisite snowflake, there is no sentience that guides it. It simply follows the path of least resistance. So too is life, and by extension, intelligence. We feel a bias towards free will because our very sense of self is derived from the ingrained feeling that our thoughts precede our actions. Oh, but do they? As the book rehashes, Libet was one of the first to test this idea emprically, and found that the sequence of electrical events in the brain that accompanied actions always began a noticeable amount of time before the conscious awareness of initiating an action. In the big picture, the vast majority of our actions are mediated by subconscious output, with a trickle of actions being refined by conscious stimuli when we have no experience with a particular situation. It is this subconscious co-opting of thought that enables us to ride a bike, walk, talk, and so on, without the need to consciously consider the steps involved. We take this for granted, but, for example, victims of stroke often find that certain actions they could once do without thinking require considerable attention if not handled automatically. We discount the idea that our actions are mainly subconscious because of the very fact that we don't consciously think about them.
That there is no free will is also an elegant explanation for the obvious lack of free will that we can witness in ourselves and others every day. How often do addicts of all kinds (food, drugs, gambling) explain that they cannot control their actions? Or what about spouses who cheat, drawn up in the "heat of the moment"? The temporary insanity plea? Tourette's syndrome? Obsessive-compulsive actions? Our own nightly dream worlds? People are willing to accept that they are not in control of many aspects of their behavior, but fail to make the obvious leap that they are indeed not in control of any of it. Having done something that they did not want to do, people then expose another aspect of the brain's process of illusory control by rationalizing their actions ("Another beer won't kill me","my spouse drove me to cheating","biting my fingernails kills the time"). This is the brain tipping its hand to the cards it's playing. When we see this in an extreme form, we call it a pathology (alcoholism, OCD). When we experience it in more mundane ways, we call it our thought process.
The book spends a lot of time on social aspects of will as well. We're much more likely to do certain things in groups, as we surrender some of our control to that of the group. An obvious example of this are religious ceremonies. People can go into trancelike, convulsive states when they are "slain in the spirit" of God, which they attribute to outside agencies. No one ever questions, however, why one is never visited by God while shopping at Radio Shack.
All that said, the illusion of will has a purpose. It may be an illusion, but it's still an effective and convincing one. While we may not really have free will, we still experience it all the same, and there is no reason that we should behave any differently knowing this. Beyond a dimunition of our sense of selves that accompanies the loss of will, I think that another reflexive disgust people feel about the concept stems from the percieved lack of responsibility that it implies. If I'm not in control, why blame me for what I do? It doesn't really work that way, however. Free will or no, social pressures will still work to modify behavior in individuals. Indeed, our existing penal system works as it does because it shapes the development of our subconscious minds. More simply, we don't even have the free will to act as if we have no free will.
So after all this, the issue is moot. It doesn't matter how we work, just that we do. Perhaps the most useful application of this knowledge will be in shaping our approach to altering bad behaviors. Knowing that we have no will, we can predict our more addictive and reflexive behaviors more accurately. Practial applications would be avoiding situations in which we might cave in to temptations. By taking action before we lose our apparent will, we co-opt the problems associated with it, and those insights are easily worth the price of this book.