This paper argues that today’s dominant understanding of secularisation — as an epochal transition from a society based on religious belief to one based on autonomous human reason — first appeared in philosophical histories at the beginning of the nineteenth century and was then anachronistically applied to early modern Europe. Apart from the earlier and persisting canon-law use of secularisation to refer to a species of exclaustration, prior to 1800 the dominant meaning of secularisation was its use in public law and diplomacy to name the civil conversion of ecclesiastical property and jurisdiction. Prior to the same point the most important use of the adjective secular was in political jurisprudence as a synonym for temporal, civil, and political, to name a religious-political settlement from which rival theologies had been excluded as the condition of its negotiation. But this usage was domain-specific, was quite compatible with religious devotion, and had nothing to do with the putatively secular character of the spheres of philosophy or the natural sciences, thence “society”. Far from seeing a shift from religious belief to autonomous rationality, early modernity in fact witnessed a significant intensification of religious belief and practice under the impact of rival confessional movements. It also emerges that the nineteenth century was characterised not by the supersession of confessional religions — or their conversion into rational religion or moral philosophy — but by their remarkable persistence and adaptation to new circumstances. In light of this, the paper argues that the variant philosophical-historical conceptions of secularisation — as the epochal supersession of religious belief by human rationality — should not be understood as theories of a putative process but as “combat concepts”. These were internal to an array of rival cultural-political factions that first emerged in early nineteenth-century Protestant Germany and that continue to do battle today
