The nature and properties of angels occupied a prominent place in medieval philosophical inquiry. Creatures of two worlds, angels provided ideal ground for exploring the nature of God and his creation, being perceived as 'models' according to which a whole range of questions were defined, from cosmological order, movement, and place, to individuation, cognition, volition, and modes of language. This collection of essays is a significant scholarly contribution to angelology, centred on the function and significance of angels in medieval speculation and its history. The unifying theme is that of the role of angels in philosophical inquiry, where each contribution represents a case study in which the angelic model is seen to motivate developments in specific areas and periods of medieval philosophical thought.