This article analyzes the compound of the categories of secularization and reoccupation in its variations from Hans Blumenberg's philosophy to Carl Schmitt's political theory and, ultimately, to Reinhart Koselleck's conceptual history. By revisiting the debate between Blumenberg and Schmitt on secularization and political theology with regard to the political-theoretical aspects of secularization and the methodological aspects of reoccupation, I will provide conceptual tools that illuminate the partly tension-ridden elements at play in Koselleck's theorizing of modernity, history, and concepts. For Schmitt, secularization is inherently related to the question of political conflict, and, correspondingly, he attempts to discredit Blumenberg's criticism of secularization as an indirectly aggressive, and thereby hypocritical, attempt to escape the political. To this end, I argue, Schmitt appropriates Blumenberg's concept of “reoccupation” and uses it alternately in the three distinct senses of “absorption,”“reappropriation,” and “revaluation.” Schmitt's famous thesis of political concepts as secularized theological concepts contains an unmistakable methodological element and a research program. The analysis therefore shows the relevance of the Blumenberg/Schmitt debate for the mostly tacit dialogue between Blumenberg and Koselleck. I scrutinize Koselleck's understanding of secularization from his early Schmittian and Löwithian theory of modernity to his later essays on temporalization of history and concepts. Despite Blumenberg's criticism, Koselleck holds onto the category of secularization throughout, but gradually relativizes it into a research hypothesis among others. Simultaneously, Koselleck formalizes, alongside other elements, the Schmittian account of reoccupation into his method of conceptual analysis and uses the term in the same three senses—thus making “reoccupation” conceptually compatible with “secularization,” despite the former notion's initial critical function in Blumenberg's theory. The examination highlights a Schmittian residue that accounts for Koselleck's reserved attitude toward Blumenberg's metaphorology, regardless of a significant methodological overlap.