At the age of eight, Karl Popper was puzzling over the idea of infinity and by fifteen beginning to take a keen interest in his father's well-stocked library of books. Unended Quest recounts these moments and many others in the life of one of the most influential thinkers of the twentieth century. Popper witnessed two World Wars and the collapse of Communism in the Eastern bloc, and provides here an indispensable account of the ideas that influenced him most, in particular his early fascination with science and philosophy.