Rudolf Carnap (1891–1970) is widely regarded as one of the most important philosophers of the twentieth century. Born in Germany and later a US citizen, he was a founder of the philosophical movement known as Logical Empiricism. He was strongly influenced by a number of different philosophical traditions (including the legacies of both Kant and Husserl), and also by the German Youth Movement, the First World War (in which he was wounded and decorated), and radical socialism. This book places his central ideas in a broad cultural, political and intellectual context, showing how he synthesised many different currents of thought to achieve a philosophical perspective that remains strikingly relevant in the twenty-first century. Its rich account of a philosopher's response to his times will appeal to all who are interested in the development of philosophy in the twentieth century.