What is, or maybe was, Europe? And might there be a nexus between the fact that specific Western institutions diffused over the globe, and global problems? The paper describes how western Christianity emerged shaping itself in a specific 'groups under roofs' structure of social relations that is described by the partition of society into groups which can easily be represented in overarching institutions. The model allows to explain the medieval European ascent, its specific development of self-governance and industrial society institutions, and the specific two-stage nature of European institutional modernization with a current second (albeit so far much less severe) modernization crisis. In a world that has become more connected and includes societies without 'groups under roofs' cultural traditions, partitioning institutions have to be reconsidered and adequately adapted.