Socio-dynamic accounts of radicalization come in many different varieties, but one idea is that group dynamics sustain and accentuate extremism and fanaticism via their impact on what group members are able to know. This chapter discusses personal journeys to extremism, group dynamics, and the alleged crippled epistemology of extremism. There are several other components of the extremist mindset that facilitate cognitive and behavioural radicalization. When describing the ways in which an extremist mindset facilitates and underpins both cognitive and behavioural radicalization, it is helpful to distinguish causes of radicalization and enabling conditions. The idea that cognitive radicalization causes psychological radicalization is not at all far-fetched. Cognitive radicalization consists in the adoption of an extremist ideology, and many such ideologies promote precisely the preoccupations, attitudes, and thinking styles that add up to an extremist mindset. Behavioural radicalization results when a small minority of cognitively radicalized individuals start to think of themselves as soldiers.