The first thing we tend to ask about people's beliefs is: are they true? We want to believe in 'the truth'. This book deals with a much more dynamic and easily addressable issue: how do our beliefs effect the world, regardless of their veracity? Our beliefs are based upon influences, the strongest of which appear to be based upon shared membership in a group, whether that be a cultural subset, a national identity, a religious identity, or a complex identity such as a participant in a scholarly discipline, or holding the identity of 'a physicist'. Movements, such as political and revolutionary identities, as well as splinter groups like self help movements, or even cults, can also serve as the nexus for an array of beliefs. Via case studies, this slim volume addresses a variety of group beliefs, who they benefit, who they disadvantage, and where they came from. Ultimately, our beliefs tell us what our needs are. This book draws upon scholarly sources, but constitutes a narrative-based inquiry open to any reader with an interest in group dynamics, and the overlap between faith and reason. This book is a above all a philosophical exploration that draws upon a variety of cross disciplinary sources to cast light upon the nature of contemporary and historical shared beliefs.