The US philosopher Sam Harris provided one of the most cynical but also scientifically accurate discussions on free will (or the absence of it). Scientific evidence shows that my consciousness is not the source of my thoughts and actions: they happen because of electrochemical events in my brain, whose causes are independent of my will. My consciousness is simply a spectator, a witness, a bystander, that later pretends to have willed those thoughts and actions. We are aware of the actions of ours that result from our neural events, but we are unaware of the neural events themselves that cause our actions. In fact, we still have to fully understand how the brain works. But most of us recognize that what we do is what the brain decides to do. Sometimes we are aware of the results (as i am now while typing these words) and sometimes we are not (unless i focus, i am not aware of my heartbeat and my breathing). We are no more in control of our thoughts than we are of our heartbeat. The only difference is that we are equipped with this weird organ of consciousness that let us be aware of the thoughts but not of the heartbeat. That's why they are called "thoughts" and not simply "neural events". Therefore the traditional distinction between voluntary and involuntary acts is illusory: all our acts are involuntary (or, voluntary if viewed from the brain's point of view). There is no difference between "premeditated" and "accidental": in both cases the person did what the brain decided to do, and that decision was made by neural processes that are not conscious based on other physical events that are beyond the control of the person. All it takes is a neurological disorder or a nutritional deficiency and our personality may change overnight. Our intention of doing something is due to neural processes in the brain that have physical causes. They are not due to our "willing" those neural processes. We will be aware of those intentions "after" the corresponding neural processes have taken place in the brain. We are unaware of the processes that cause our intentions, and we are unaware of the processes that caused those processes. Therefore we cannot be considered "responsible" for those intentions and for the actions that follow them. Murderers, rapists and sociopaths have no choice but to do what their brains order their bodies to do. You would do the same if you had their brain. You can view them as mere witnesses of their body's horrible acts or as the victims of physical processes and causes that they cannot possibly alter. Scientists who introduce the "chance" of Quantum Mechanics don't change the scenario by much: if there is an element of chance in what my brain decides to do, i can hardly be considered responsible for that chance. By definition, "chance" is not something that i decided. If the world is fully deterministic, there is nothing that i can do to keep my brain from doing what it will do. If the world is driven by chance, there is equally nothing that i can do to keep my brain from doing what it will do. Either way, i am not responsible for what i do. Either our wills are determined by physical causes and we are not responsible for them or they are the product of chance events in which case we are not responsible for them. We are not responsible for what we do because we are mere witnesses, spectators, bystanders. The real cause of our behavior (the infinite chain of physical events that led to the brain to be in such and such a state) is hidden from our consciousness. Our consciousness simply takes note of what that behavior is. Harris therefore argues that morality is bogus. We cannot blame a murderer, a rapist or a sociopath: they do what their brains tell them to do. In a sense, we should feel sorry for them just like we feel sorry for someone who has a brain tumor or Lyme disease. However, Harris argues that we can asses more rationally the dangers posed by a brain. Whatever caused the brain to behave the way it does (genes, upbringing, life events), how likely is that brain to cause more harm to other humans? Basically, Harris is arguing that "evil" is nothing more than an algorithm. The conscious person is not "guilty" of her crimes, but her brain may pose a risk to society. It is not a matter of "punishment" but of "prevention". The difference between being killed by a fellow human or being killed by an earthquake is that we can prevent the human if we know that she is prone to killing. Harris wants to "punish" people for pragmatic reasons, not for moral reasons.