Solidarity can be conceived in multiple ways. This article probes possible underlying ontological and normative assumptions of solidarity. In order to conceptually clarify the notion of solidarity, we distinguish between five types of solidarity. We suggest that solidarity is either grounded in the Enlightenment ideas of liberty, or a category of loyalty and allegiance. If the former is the case, solidarity can be justified on rational grounds. If the latter is the case, it is contingent on narratives of historical continuity and a non-rational sense of belonging. Moreover, we show that different types of solidarity can be derived from Anglo-Saxon and continental thought, which hints at different conceptions of community.