This is the first comprehensive study of the philosophical achievements of twelfth-century Western Europe. It is the collaboration of fifteen scholars whose detailed survey makes accessible the intellectual preoccupations of the period, with all texts cited in English translation throughout. After a discussion of the cultural context of twelfth-century speculation, and some of the main streams of thought - Platonic, Stoic, and Arabic - that quickened it, comes a characterisation of the new problems and perspectives of the period, in scientific inquiry, speculative grammar, and logic. This is followed by a closer examination of the distinctive features of some of the most innovative thinkers of the time, from Anselm and Abelard to the School of Chartres. A final section shows the impact of newly recovered works of Aristotle in the twelfth-century West.