My aim is to explore a possible means of enlarging our present understanding of the concepts we employ in social and political argument. The prevailing orthodoxy bids us proceed by consulting our intuitions about what can and cannot be coherently said and done with the terms we generally use to express the concepts involved. But this approach might with profit be supplemented, I shall argue, if we were to confront these intuitions with a more systematic examination of the unfamiliar theories within which even our most familiar concepts have sometimes been put to work at different historical periods.

One way of proceeding with this line of thought would be to offer a general defence of this view about the ‘relevance’ of the history of philosophy for the understanding of contemporary philosophical debates. But I shall instead attempt to make a more direct, if more modest, contribution to the theme of the present volume by focusing on one particular concept which is at once central to current disputes in social and political theory and is at the same time overdue, it seems to me, for this type of historical treatment.

The concept I have in mind is that of political liberty, the extent of the freedom or liberty of action available to individual agents within the confines imposed on them by their membership of political society. The first point to be observed is that, among English-speaking philosophers of the present time, the discussion of this topic has given rise to one conclusion which commands a remarkably wide measure of assent.