This is an open access title available under the terms of a CC BY NC ND 4.0 International license. It is free to read at Oxford Scholarship Online and offered as a free PDF download from OUP and selected open access locations. Why does the mind matter for collective action? In Contentious Minds, Florence Passy and Gian-Andrea Monsch explain how cognitive and relational processes allow activists participate in and sustain their commitment to activism. Based on a wide array of survey and interview data with activists engaged in protest, volunteering and unions, they highlight how a commitment community develop shared values, identities, and meanings through interaction. The interplay of talk and ties enables stories and meanings to be constructed and exchanged, conveys worldviews and intentions that are modified through ongoing conversations, and reinforces and maintains commitment over time. Passy and Monsch's ambitious work brings the mind and culture back into the study of social movements and highlights the crucial role social networks play in constructing the communities and shared values that sustain commitment.