Berlin, Isaiah. Political Ideas in the Romantic Age: Their Rise and Influence on Modern Thought. Princeton: Princeton University Press, 2006. Originally composed between 1950 and 1952, Political Ideas in the Romantic Age (hereafter PIRA) was initially delivered by Isaiah Berlin at Bryn Mawr College as the Mary Flexner Lectures in 1952. PIRA not only represents Berlin's longest continuous text, it also contains in embryonic form most of the ideas found in Berlin's mature work: positive and negative liberty, his analysis of the philosophy of history, his critique of determinism, and his account of the Enlightenment and its varied critics and successors. As such, PIRA represents a key stage in the development of Berlin's political thought and its greatest value lies in its ability to speak to the question of whether or not Berlin can be understood as a systematic political thinker.