Abstract
Abstract This paper analyses the rise of radical movements and the design of counter-radicalisation policies. A group derives meaning from participation in identity-based activities and a forward-looking organisation provides a platform for these activities. The warning sign for radicalisation is cultural purification by the organisation, i.e., the screening out of moderates and exclusive recruitment of radicals. While this shrinks the club, it puts it on a growth path along which it becomes larger and more extreme over time. Conventional counter-radicalisation policies can backfire. The radicalisation mechanisms we identify can be disabled by mild anti-radical messaging and informational interventions that eliminate stereotypes.