The Prisoner's Dilemma

Mutual cooperation beats mutual defection, but defecting is the better move whatever the other side does.

The defining feature is a dominant strategy, which is what makes it a trap rather than a hard problem: reasoning harder does not help, because both parties are already reasoning correctly. It appears wherever an individually rational move is collectively destructive — discounting, overfishing, doping, arms build-ups, cutting safety margins to stay competitive. Crucially, the outcome is stable. Exposure does not fix it, and neither does everybody agreeing it is bad.

How it feels

• Both sides say, privately, that they would rather this stopped.
• Whoever moves first alone is worse off — and everyone knows it.
• The situation survives being exposed. Everyone already knows.
• Any single participant who unilaterally behaves better simply loses.

Who is playing

The two obvious parties, plus — almost always forgotten — whoever could enforce an agreement between them. The absence of that third party IS the game. Add a credible enforcer and the shape disappears.

Where it lands

Mutual defection, indefinitely, with both sides worse off than an achievable alternative and neither able to move first.

What moves it

Change the payoffs or change the structure — a binding contract, an enforcement body, a repeated relationship, transparency that creates reputational cost, or a subsidy that flips the ranking. Appeals to conscience reliably fail here because nobody is behaving badly.

Not to be confused with

Nearly every misread in practice is a shape mistaken for its neighbour — and each of those mistakes points you at the wrong fix.

Where you have already met it