Two hunters can bag a stag together, or a hare alone. What do you pick?
You and a partner can each choose to hunt a stag or a hare. Hunting the stag only works if you both commit, and it feeds you both well. Hunting a hare works alone but feeds you less. If you commit to the stag and your partner bails for the hare, you get nothing. What's the smart move?
Reveal the answer
Both outcomes — everyone chasing the stag, or everyone safely taking a hare — are stable equilibria; neither player can do better by switching alone. The puzzle, traced to a passage in Rousseau's Discourse on Inequality and later formalized in game theory, shows that even when full cooperation is better for everyone, trust alone can make the safer, lonelier option the rational one to pick.
— Jean-Jacques Rousseau, Discourse on the Origin and Basis of Inequality Among Men — 1755