Why do thinkers hostile or agnostic toward Christianity find in its apocalyptic doctrines—often seen as bizarre—appealing tools for interpreting politics? This article tackles that puzzle. First, it clarifies the concept of secular apocalyptic thought and its relation to Christianity. I propose that, to avoid imprecision, the study of secular apocalyptic thought should focus on cases where religious apocalyptic thought's influence on secular thinkers is clear because they explicitly reference such thought and its appeal (e.g. Engels's fascination with Christian apocalyptic thought). Second, it argues that the political appeal of apocalyptic thought—and, specifically, what I term cataclysmic apocalyptic thought (CAT)—partly lies in offering resources to navigate persistent challenges in ideal theory. The ideal theorist faces competing goals: formulating an ideal that is utopian and feasible. One potential approach to this challenge is CAT, which embraces a utopian ideal and declares it feasible through identifying crisis as the vehicle to realize it.