“If the atoms never swerve so as to originate some new movement that will snap the bonds of fate, the everlasting sequence of cause and effect—what is the source of the free will possessed by living things throughout the earth?”—Titus Lucretius Carus, Roman philosopher and poet, 99–55 BC.


Human free will might seem like the squishiest of philosophical subjects, way beyond the realm of mathematical demonstration. But two highly regarded Princeton mathematicians, John Conway and Simon Kochen, claim to have proven that if humans have even the tiniest amount of free will, then atoms themselves must also behave unpredictably.

The finding won’t give many physicists a moment’s worry, because traditional interpretations of quantum mechanics embrace unpredictability already. The best anyone can hope to do, quantum theory says, is predict the probability that a particle will behave in a certain way.

But physicists all the way back to Einstein have been unhappy with this idea. Einstein famously grumped, “God does not play dice.” And indeed, ever since the birth of quantum mechanics, some physicists have offered alternate interpretations of its equations that aim to get rid of this indeterminism. The most famous alternative is attributed to the physicist David Bohm, who argued in the 1950s that the behavior of subatomic particles is entirely determined by “hidden variables” that cannot be observed.

Conway and Kochen say this search is hopeless, and they claim to have proven that indeterminacy is inherent in the world itself, rather than just in quantum theory. And to Bohmians and other like-minded physicists, the pair says: Give up determinism, or give up free will. Even the tiniest bit of free will.