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.
Carlo Rovelli's Edge Bio Page
THE REALITY CLUB: Lee Smolin
A PHYSICIST LOOKS AT FREE WILL, DETERMINISM, QUANTUM THEORY AND STATISTICAL FLUCTUATIONS
Since Democritus suggested that the world can be seen as the result of accidental clashing of atoms, the question of free will has disturbed the sleeps of the naturalist: how to reconcile the deterministic dynamics of the atoms with man's freedom to choose? Modern physics has altered the data a bit, and the ensuing confusion requires clarification.
Democritus assumed the movement of atoms to be deterministic: a different future does not happen without a different present. But Epicurus, who in physical matters was a close follower of Democritus, had already perceived a difficulty between this tight determinism and human freedom, and modified the physics of Democritus, introducing an element of indeterminism at the atomic level.
The new element was called "clinamen." The "clinamen" is a minimum deviation of an atom from its natural rectilinear path, which takes place in a completely random fashion. Lucretius, who presents the Democritean-Epicurean theory in his poem, "De Rerum Natura", "On Things Of Nature," notes in poetic words: the deviation from straight motion happens "uncertain tempore ... incertisque loci ", in an uncertain time and an uncertain place [Liber II, 218].
A very similar oscillation between determinism and indeterminism has happened again in modern physics. Newton's atomism is deterministic in a similar manner as Democritus's. But at the beginning of the twentieth century, Newton's equations have been replaced by those of quantum theory, which bring back an element of indeterminism, quite similar, in fact, to Epicurus's correction of Democritus's determinism. At the atomic scale, the motion of the elementary particles is not strictly deterministic.
Can there be a relationship between this atomic-scale quantum indeterminism and human freedom to choose?