The purpose of this book is not to produce a comprehensive history of Scottish unionism as a political phenomenon, but to offer a taxonomy of Scottish unionist discourses from the vantage point of the historian of political thought. Indeed, the book is an expanded version of the Carlyle Lectures in the History of Political Thought given in the University of Oxford during Hilary Term 2006 under the title, ‘The varieties of unionism in Scottish political thought, 1707–1974’. I am grateful to the Carlyle Electors for their invitation, and particularly to George Garnett, who organised the social side of things, including the Carlyle Dinner, and to Peter Ghosh, who steered me towards the neglected topic of Scottish unionism. I also feel an enormous debt to the Warden and Fellows of All Souls who took the opportunity presented by the Carlyle Lectures to rescue me from a prolonged period of quondamnation. Several Fellows of the College were staunch supporters of the lecture series, and I owe special thanks to the political scientists, Peter Pulzer and Chris Hood, for congenial discussions of problems beyond the immediate ken of the historian, to Fergus Millar for generous support on several fronts and to Charles and Carol Webster and the wider Webster family for their kindness and hospitality. Elsewhere in Oxford John Robertson and Brian Young welcomed my participation in the wider life of the University, and I have very fond memories of the seminars at the Voltaire Foundation.