Rosalind English in The Guardian:
The US neuroscientist Sam Harris claims in a new book that free will is such a misleading illusion that we need to rethink our criminal justice system on the basis of discoveries coming from the neurological wards and MRI scans of the human brain in action.
The physiologist Benjamin Libet famously demonstrated in the 1980s that activity in the brain's motor regions can be detected some 300 milliseconds before a person feels that he has decided to move. Subjects were hooked up to an EEG machine and were asked to move their left or right hand at a time of their choosing. They watched a specially designed clock to notice what time it was when they were finally committed to moving their left or right hand. Libet measured the electrical potentials of their brains and discovered that nearly half a second before they were aware of what they were going to do, he was aware of their intentions. Libet's findings have been borne out more recently in direct recordings of the cortex from neurological patients. With contemporary brain scanning technology, other scientists in 2008 were able to predict with 60% accuracy whether subjects would press a button with their left or right hand up to 10 seconds before the subject became aware of having made that choice (long before the preparatory motor activity detected by Libet).
Clearly, findings of this kind are difficult to reconcile with the sense that one is the conscious source of one's actions. The discovery that humans possess a determined will has profound implications for moral responsibility. Indeed, Harris is even critical of the idea that free will is “intuitive”: he says careful introspection can cast doubt on free will. In an earlier book on morality, Harris argues
Thoughts simply arise in the brain. What else could they do? The truth about us is even stranger than we may suppose: The illusion of free will is itself an illusion (The Moral Landscape)
But a belief in free will forms the foundation and underpinning of our enduring commitment to retributive justice. The US supreme court has called free will a “universal and persistent” foundation for our entire system of law.