The contributors to this volume discuss and for the most part challenge whether many minds can be wiser than one.

1. Collective wisdom: old and new Hélène Landemore; 2. Prediction markets: trading uncertainty for collective wisdom Emile Servan-Schreiber; 3. Designing wisdom through the web: the passion of ranking Gloria Origgi; 4. Some microfoundations of collective wisdom Scott Page and Lu Hong; 5. What has collective wisdom to do with wisdom? Daniel Andler; 6. Legislation, planning, and deliberation John Ferejohn; 7. Epistemic democracy in classical Athens: sophistication, diversity, and innovation Josiah Ober; 8. The optimal design of a constituent assembly Jon Elster; 9. Sanior pars and major pars in the contemporary aeropagus: medicine evaluation committees in France and the United States Philippe Urfalino; 10. Collective wisdom: lessons from the theory of judgment aggregation Christian List; 11. Democracy counts: should rulers be numerous? David Estlund; 12. Democratic reason: the mechanisms of collective intelligence in politics Hélène Landemore; 13. Rational ignorance and beyond Gerry Mackie; 14. The myth of the rational voter and political theory Bryan Caplan; 15. Collective wisdom and institutional design Adrian Vermeule; 16. Reasoning as a social competence Dan Sperber and Hugo Mercier; 17. Conclusion Jon Elster.