In his inaugural lecture on the study of history, delivered at Cambridge in 1895, Lord Acton exhorted his students to ‘try others by the final maxim that governs your own lives, and to suffer no man and no cause to escape the undying penalty which history has the power to inflict on wrong … If we lower our standard in history, we cannot uphold it in Church and State.’

This was Acton in his seventh decade, some seven years before his death. As a young man in his mid twenties, writing for The Rambler, which at that time Acton and his circle of liberal catholics hoped to use as the vehicle for educating their co-religionists into harmonizing their ancient faith with contemporary science and scholarship, he struck a very different note. This was the Acton who distinguished between Catholic and Protestant intolerance, excusing the former as the product of ‘external circumstances,’ while condemning the latter as an ‘imperative precept and a part of its doctrine.’ Acton was not, at any point in his life, a conventional thinker, and just as his later view of the historian as moral judge was, and remains, controversial, so his earlier reading of ecclesiastical history was disputed by friend and foe.