I’ve been reading Epictetus, the 2nd-century Stoic philosopher. His words have unsettled me: we control almost nothing. He says, “Some things are up to us, and some are not. Up to us are judgment, inclination, desire, aversion—in short, whatever is our own doing. Not up to us are our bodies, possessions, reputations, public offices—in short, whatever is not our own doing.”

Demis Hassabis was a chess prodigy at the age of four. By his early teens, he competed at the highest levels and could have pursued a comfortable, prestigious life in that narrow domain. But at thirteen, he did something unusual: he walked away.