Leslie Stephen (1832-1904), author, literary critic, social commentator and the first editor of the Dictionary of National Biography, published his two-volume History of English Thought in the Eighteenth Century (also reissued in this series) in 1876. This led him to further investigation and study of utilitarianism, whose proponents believed that human action should be guided by the principle of ensuring the happiness of the greatest number of people. While working on many other projects, especially the Dictionary, and haunted by domestic tragedy in the sudden death of his second wife in 1895, Stephen struggled for two decades with this undertaking, calling it the ‘utilitarian bog’: the long-awaited three-volume work was finally published in 1900. Volume 3 examines John Stuart Mill (1806-73), the son of James Mill, philosopher, economist and a proponent of utilitarianism who was influential in the development of political liberalism.