Any attempt to link this discussion to moral, ethical or legal issues, as is often been done, is pure nonsense. The fact that it is possible to say that a criminal has been driven to kill because of the ways in which Newton's laws have acted on the molecules of his body has nothing to do either with the opportunity of punishment, nor with the moral condemnation. It is respecting those same laws by Newton that putting criminals in jail reduces the murders, and it is respecting those same laws by Newton that society as a whole functions, including its moral structure, which in turn determines behavior. There is no contradiction between saying that a stone flew into the sky because a force pushed it, or because a volcano exploded. In the same manner, there is no contradiction in saying we do not commit murder because something is encoded in the decision-making structure of our brain or because we are bound by a moral belief.
Free will has nothing to do with quantum mechanics. We are deeply unpredictable beings, like most macroscopic systems. There is no incompatibility between free will and microscopic determinism. The significance of free will is that behavior is not determined by external constraints, not by the psychological description of our neural states to which we access. The idea that free will may have to do with the ability to make different choices on equal internal states is an absurdity, as the ideal experiment I have described above shows. The issue has no bearing on questions of a moral or legal nature. Our idea of being free is correct, but it is just a way to say that we are ignorant on why we make choices.
CARLO ROVELLI is a theoretical physicist, working on quantum gravity and on foundations of spacetime physics. He is Professor of Physics at Centre De Physique Théorique De Luminy at Aix-Marseille University, France and member of the Intitut Universitaire de France. He is the author of The First Scientist: Anaximander and His Legacy; and Quantum Gravity.
To read more, click here.