system of events, to determine the consequent probability of any other event logically connected with those events. Death In late November 1864, Boole walked, in heavy rain, from his home at Lichfield Cottage in Ballintemple to the university, a distance of three miles, and lectured wearing his wet clothes. He soon became ill, developing pneumonia. As his wife believed that remedies should resemble their cause, she wrapped him in wet blankets – the wet having brought on his illness. Boole's condition worsened and on 8 December 1864, he died of fever-induced pleural effusion. He was buried in the Church of Ireland cemetery of St Michael's, Church Road, Blackrock (a suburb of Cork). There is a commemorative plaque inside the adjoining church. Legacy Boole is the namesake of the branch of algebra known as Boolean algebra, as well as the namesake of the lunar crater Boole. The keyword Bool represents a Boolean datatype in many programming languages, though Pascal and Java, among others, both use the full name Boolean. The library, underground lecture theatre complex and the Boole Centre for Research in Informatics at University College Cork are named in his honour. A road called Boole Heights in Bracknell, Berkshire is named after him. 19th-century development Boole's work was extended and refined by a number of writers, beginning with William Stanley Jevons, who also authored the article about Boole in the Encyclopaedia Britannica. Augustus De Morgan had worked on the logic of relations, and Charles Sanders Peirce integrated his work with Boole's during the 1870s. Other significant figures were Platon Sergeevich Poretskii, and William Ernest Johnson. The conception of a Boolean algebra structure on equivalent statements of a propositional calculus is credited to Hugh MacColl (1877), in work surveyed 15 years later by Johnson. Surveys of these developments were published by Ernst Schröder, Louis Couturat, and Clarence Irving Lewis. 20th-century development In 1921, the economist John Maynard Keynes published a book on probability theory, A Treatise of Probability. Keynes believed that Boole had made a fundamental error in his definition of independence which vitiated much of his analysis. In his book The Last Challenge Problem, David Miller provides a general method in accord with Boole's system and attempts to solve the problems recognised earlier by Keynes and others. Theodore Hailperin showed much earlier that Boole had used the correct mathematical definition of independence in his worked out problems. Boole's work and