Harris says the idea of free will "cannot be mapped on to any conceivable reality" and is incoherent.^[5][6] According to Harris, science "reveals you to be a biochemical puppet."^[7] People's thoughts and intentions, Harris says, "emerge from background causes of which we are unaware and over which we exert no conscious control." Every choice we make is made as a result of preceding causes. These choices we make are determined by those causes, and are therefore not really choices at all. Furthermore, as thoughts arise from causes that we cannot control, our actions influenced by these thoughts are also uncontrollable. Harris also draws a distinction between conscious and unconscious reactions to the world. Even without free will, consciousness has an important role to play in the choices we make. Harris argues that this realization about the human mind does not undermine morality or diminish the importance of social and political freedom, but it can and should change the way we think about some of the most important questions in life.

Sam Harris in his book explains:^[8]

Consider the following examples of human violence:

1. A four-year-old boy was playing with his father’s gun and killed a young woman. The gun had been kept loaded and unsecured in a dresser drawer.

2. A 12-year-old boy who had been the victim of continual physical and emotional abuse took his father’s gun and intentionally shot and killed a young woman because she was teasing him.

3. A 25-year-old man who had been the victim of continual abuse as a child intentionally shot and killed his girlfriend because she left him for another man.

4. A 25-year-old man who had been raised by wonderful parents and never abused intentionally shot and killed a young woman he had never met “just for the fun of it.”

5. A 25-year-old man who had been raised by wonderful parents and never abused intentionally shot and killed a young woman he had never met “just for the fun of it.” An MRI of the man’s brain revealed a tumor the size of a golf ball in his medial prefrontal cortex (a region responsible for the control of emotion and behavioral impulses).

In each case a young woman died, and in each case her death was the result of events arising in the brain of another human being. But the degree of moral outrage we feel depends on the background conditions described in each case. We suspect that a four-year-old child cannot truly kill someone on purpose and that the intentions of a 12-year-old do not run as deep as those of an adult. In cases 1 and 2, we know that the brain of the killer has not fully matured and that not all the responsibilities of personhood have yet been conferred. The history of abuse and the precipitating circumstance in case 3 seem to mitigate the man’s guilt: This was a crime of passion committed by a person who had himself suffered at the hands of others. In 4 there has been no abuse, and the motive brands the perpetrator a psychopath. Case 5 involves the same psychopathic behavior and motive, but a brain tumor somehow changes the moral calculus entirely: Given its location, it seems to divest the killer of all responsibility for his crime. And it works this miracle even if the man’s subjective experience was identical to that of the psychopath in case 4—for the moment we understand that his feelings had a physical cause, a brain tumor, we cannot help seeing him as a victim of his own biology.

How can we make sense of these gradations of moral responsibility when brains and their background influences are in every case, and to exactly the same degree, the real cause of a woman’s death?

We need not have any illusions that a causal agent lives within the human mind to recognize that certain people are dangerous. What we condemn most in another person is the conscious intention to do harm. Degrees of guilt can still be judged by reference to the facts of a case: the personality of the accused, his prior offenses, his patterns of association with others, his use of intoxicants, his confessed motives with regard to the victim, etc. If a person’s actions seem to have been entirely out of character, this might influence our view of the risk he now poses to others. If the accused appears unrepentant and eager to kill again, we need entertain no notions of free will to consider him a danger to society.

Why is the conscious decision to do another person harm particularly blameworthy? Because what we do subsequent to conscious planning tends to most fully reflect the global properties of our minds—our beliefs, desires, goals, prejudices, etc. If, after weeks of deliberation, library research, and debate with your friends, you still decide to kill the king—well, then killing the king reflects the sort of person you really are. The point is not that you are the ultimate and independent cause of your actions; the point is that, for whatever reason, you have the mind of a regicide.

Certain criminals must be incarcerated to prevent them from harming other people. The moral justification for this is entirely straightforward: Everyone else will be better off this way. Dispensing with the illusion of free will allows us to focus on the things that matter—assessing risk, protecting innocent people, deterring crime, etc. However, certain moral intuitions begin to relax the moment we take a wider picture of causality into account. Once we recognize that even the most terrifying predators are, in a very real sense, unlucky to be who they are, the logic of hating (as opposed to fearing) them begins to unravel. Once again, even if you believe that every human being harbors an immortal soul, the picture does not change: Anyone born with the soul of a psychopath has been profoundly unlucky.

Why does the brain tumor in case 5 change our view of the situation so dramatically? One reason is that its influence has been visited upon a person who (we must assume) would not otherwise behave in this way. Both the tumor and its effects seem adventitious, and this makes the perpetrator appear to be purely a victim of biology. Of course, if we couldn’t cure his condition, we would still need to lock him up to prevent him from committing further crimes, but we would not hate him or condemn him as evil. Here is one front on which I believe our moral intuitions must change: The more we understand the human mind in causal terms, the harder it becomes to draw a distinction between cases like 4 and 5.

The book has been the subject of criticism.^{[9][10][4][11]} For example, in a critical review, philosopher and cognitive scientist Daniel Dennett argued that Free Will attacks only the "popular" idea of free will, which Dennett accepts to be flawed. He states that "improvements" to the popular idea of free will exist and that Harris should have instead addressed these.^[12] Harris published a response.^[13]

• Immanuel Kant
• Neuroscience of free will
• Decision making