This book presents an innovative new way of thinking about transmission media: through the figure of the messenger as a key metaphor. It explores a strikingly diverse range of types of transmission, including the circulation of money, the translation of languages, angelic visitations, the spread of infectious disease, the transferences that occur in psychoanalysis, the act of bearing witness, and the development of cartography. In each case, Sybille Krämer uses the insight offered by the metaphor of the messenger to help explain and explore the field of media philosophy and the ways that mediation shapes our understanding of the world around us.