The purpose of this paper is to examine the logics of justification embedded in the discourse of radical Islam and fundamentalist Christianity. Proponents of either side mostly suggest that their ideological system stands in opposition to the other. But such opposition holds only for the substantive content of these religious ideologies, not necessarily their underlying logics. That is, they indeed worship different deities, practice different customs and rituals, and in many respects, see the world in very different ways. However, our analysis examines the logical construction of their respective ideological discursive justifications, finding that differences in content are nonetheless underpinned by a remarkably similar system of logic. Previous comment on underlying similarities between these religions has been based on a sense of their affective tenor, observations of their similar rhetoric and methods of activism and otherwise random fragments of coincidence. We instead apply an ontological schema to paradigmatic discursive examples of each, thereby illustrating that their core logics are fundamentally the same. © 2011 Taylor & Francis.