John Emerich Edward Dalberg Acton, 1st Baron Acton of Aldenham, 8th Baronet, known as Lord Acton, was an English Catholic Liberal historian called "the magistrate of history." He was one of the greatest personalities of the 19th century and was considered the most learned Englishman of his day. The history of freedom was his life's work, and he was the first great modern philosopher of resistance to the power of the evil state. In 1870, when the First Vatican Council announced the doctrine of papal infallibility, Lord Acton was all but excommunicated for opposing it. A comment that he wrote in a letter, "Power tends to corrupt, and absolute power corrupts absolutely," has come down to us as a famous aphorism. He also said, "The great novelty of the American Constitution was that it imposed checks on the representatives of the people." In 1895, he was appointed Regius Professor of Modern History at Cambridge University. Most of his written work consisted of essays and copies of his lectures. In 1899 and 1900, Lord Acton coordinated the development of The Cambridge Modern History, a monumental work of detailed, collaborative scholarship. He served as a Member of Parliament and as an adviser and friend to Prime Minister William Gladstone. In 1865 he married Marie von Arco-Valley, with whom he had four children. He succeeded to the baronetcy in 1837, and was raised to the peerage in 1869.