This is the first full-length study of Lord Acton's History of Liberty. It is the first edited text of Lord Acton's notes made towards one of the great unwritten books of the nineteenth century. Herbert Butterfield once described Acton as 'by far the greatest historical thinker that England has ever had'. A friend of Gladstone and a member first of the House of Commons and then of the Lords, he accumulated a vast library, most of which is now in the University Library at Cambridge. It represents a man of cosmopolitan interests, both as a campaigner against Papal Infallibility and then, after 1870, for liberal causes. George Watson's text is a full account of the surviving books and papers. Acton's projected masterpiece, however, - the history of liberty on which he worked intensively, mainly in the years 1877 to 1883 - never emerged beyond a series of notes. In this book, George Watson presents a text of those notes. They offer many examples of Acton's liberal philosophy and epigrammatic style.