Talk about identity has become ubiquitous. The list of things that are said to have an identity is almost endless. The Introduction explains that identity is all about sameness and difference, but it’s not simple: ‘identity’ means different things to different people and in different disciplines. Identities are both things that must be explained and things that are invoked to explain. As the concept is understood nowadays, it is first of all rooted in the ideology of the French and American revolutions that celebrated the dignity and equality of the individual. This VSI does not concentrate on the different meanings of ‘identity’, but on why identity is important in so many different fields.