During the Scottish Revolution (1637-1651), royalists and Covenanters appealed to Scottish law, custom and traditional views on kingship to debate the limits of King Charles I's authority. But they also engaged with the political ideas of sixteenth- and seventeenth-century Protestant and Catholic intellectuals beyond the British Isles. This book explores the under-examined European context for Scottish political thought by analysing how royalists and Covenanters adapted Lutheran, Calvinist, and Catholic political ideas to their own debates about church and state. In doing so, it argues that Scots advanced languages of political legitimacy to help solve a crisis about the doctrines, ceremonies and polity of their national church. It therefore reinserts the importance of ecclesiology to the development of early modern political theory.