There are 20 books in this series, sold separately, but together forming an accessible introduction to the history of Western thought. Ranging from Seneca's On The Shortness Of Life to George Orwell's Why I Write, each neat, pocket-sized book contains a philosophical tract or piece of political writing that in some way changed the course of history. Some are well known - Virginia Woolf's feminist polemic A Room Of One's Own; others well known but barely read, such as Arthur Schopenhauer's On The Suffering Of The World. You can accuse Penguin of dumbing-down philosophy with a marketing ploy, but you cannot deny that the project is a great idea.