By Carlo Rovelli
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in a similar manner as Democritus’s. But at the beginning of the twentieth century, Newton’s equations have been replaced by those of quantum theory, which bring back an element of indeterminism, quite similar, in fact, to Epicurus’s correction of Democritus’s determinism.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?
The idea has been proposed, and often reappears, but is not credible, for two reasons. The first is that the indeterminism of quantum mechanics is governed by a rigorous probabilistic dynamics. The equations of quantum mechanics do not determine what will happen, but determine strictly the probability of what will happen. In other words, they certify that the violation of determinism is strictly random. This goes in exactly the opposite direction from human freedom to choose. If human freedom to choose was reducible to quantum indeterminism, then we should conclude that human choices are strictly regulated by the chance. Which is the opposite of the idea of freedom of choice. The indeterminism of quantum mechanics is like throwing a coin to see if it falls heads or tails, and act accordingly. This is not this what we call freedom to choose. click link for full article;