Sam Harris over at his blog (via Andrew Sullivan):
We are conscious of only a tiny fraction of the information that our brains process in each moment. While we continually notice changes in our experience—in thought, mood, perception, behavior, etc.—we are utterly unaware of the neural events that produce these changes. In fact, by merely glancing at your face or listening to your tone of voice, others are often more aware of your internal states and motivations than you are. And yet most of us still feel that we are the authors of our own thoughts and actions.
The problem is that no account of causality leaves room for free will—thoughts, moods, and desires of every sort simply spring into view—and move us, or fail to move us, for reasons that are, from a subjective point of view, perfectly inscrutable. Why did I use the term “inscrutable” in the previous sentence? I must confess that I do not know. Was I free to do otherwise? What could such a claim possibly mean? Why, after all, didn’t the word “opaque” come to mind? Well, it just didn’t—and now that it vies for a place on the page, I find that I am still partial to my original choice. Am I free with respect to this preference? Am I free to feel that “opaque” is the better word, when I just do not feel that it is the better word? Am I free to change my mind? Of course not. It can only change me.
There is a distinction between voluntary and involuntary actions, of course, but it does nothing to support the common idea of free will (nor does it depend upon it). The former are associated with felt intentions (desires, goals, expectations, etc.) while the latter are not. All of the conventional distinctions we like to make between degrees of intent—from the bizarre neurological complaint of alien hand syndrome to the premeditated actions of a sniper—can be maintained: for they simply describe what else was arising in the mind at the time an action occurred. A voluntary action is accompanied by the felt intention to carry it out, while an involuntary action isn’t. Where our intentions themselves come from, however, and what determines their character in every instant, remains perfectly mysterious in subjective terms. Our sense of free will arises from a failure to appreciate this fact: we do not know what we will intend to do until the intention itself arises. To see this is to realize that you are not the author of your thoughts and actions in the way that people generally suppose. This insight does not make social and political freedom any less important, however. The freedom to do what one intends, and not to do otherwise, is no less valuable than it ever was.
While all of this can sound very abstract, it is important to realize that the question of free will is no mere curio of philosophy seminars. A belief in free will underwrites both the religious notion of “sin” and our enduring commitment to retributive justice.