The aim and effect of transnational terrorism today - stemming from both Islamic revivalism and ethno-nationalist resurgence - are to fragment social consensus by forcing people into opposing camps, with no room for innocents. Governments and peoples wrestle with why this is happening and what to do. At issue here: Can social science, specifically psychology, be helpful? A partial answer focuses on recent contributions from behavioral and brain studies into how 'devoted actors', committed to non-negotiable 'sacred values' and the groups those values are embedded in, resort to extreme violence and resist rational-actor approaches to conflict resolution when opposing values are involved. Alternatives approaches emphasize reckoning with sacred values rather than disregarding them, and social counter-engagement instead of reliance on socially disembodied counter-narratives.