'A definitive work...explains clearly and succinctly concepts and theories at the heart of European and American philosophy.' - Brenda Almond. What do philosophers mean by 'absolute' and 'akrasia'? What are 'Polish notation' and 'prime matter'? What contributions to human thought were made by Plato, Machiavelli, Kant and Derrida? These questions and many more are answered by this illuminating dictionary, which draws on contributions from over 100 leading philosophers.