The following essay is an extended version of the Inaugural Lecture I delivered in the University of Cambridge on 12 November 1997 as Regius Professor of Modern History. I have tried to sketch the rise and fall within Anglophone political theory of what I have labelled a neo-roman understanding of civil liberty. The neo-roman theory rose to prominence in the course of the English revolution of the mid-seventeenth century. Later it was used to attack the ruling oligarchy of eighteenth-century Britain, and still later to defend the revolution mounted by the American colonists against the British crown. During the nineteenth century, however, the neo-roman theory increasingly slipped from sight. Some elements survived in the Six Points of the Chartists, in John Stuart Mill's account of the subjection of women, and in other pleas on behalf of the dependent and oppressed. But the ideological triumph of liberalism left the neo-roman theory largely discredited. Meanwhile the rival view of liberty embedded in classical liberalism went on to attain a predominance in Anglophone political philosophy which it has never subsequently relinquished. The ambition of the following essay is to question this liberal hegemony by attempting to re-enter the intellectual world we have lost. I try to situate the neo-roman theory within the intellectual and political contexts in which it was initially formulated, to examine the structure and presuppositions of the theory itself, and thereby to provide us with the means to think again, if we will, about its possible claims on our intellectual allegiances.