Karl Popper is regarded by many commentators as the greatest philosopher of the twentieth century. His most significant work is found in his first four published books--Logik der Forschung: Zur Erkenntnistheorie der modernen Naturwissenschaft (Logic of Discovery: Toward an Epistemology of Modern Natural Science, 1935; translated as The Logic of Scientific Discovery, 1959), The Open Society and Its Enemies (1945), The Poverty of Historicism (1957), and Conjectures and Refutations: The Growth of Scientific Knowledge (1962)--which attack fundamental problems with ferocious integrity, clarity, simplicity, and originality. They have wide and fruitful implications for science, philosophy, the social sciences, education, art, political philosophy, and practical politics. A volume of The Library of Living Philosophers series (1974) is devoted to Popper's work; like all volumes in the series, it includes the subject's intellectual autobiography. Popper's was published separately, with revisions, as Unended Quest: An Intellectual Autobiography (1976).

Karl Raimund Popper was born in Vienna on 28 July...