This book presents two lost histories. One relates to the biography of the Vienna Circle-philosopher Otto Neurath (1882-1945) whose life-story reflects the tumultuous early twentieth century, the other to the history of museums, exhibitions, and of audience advocacy. A polymath, Neurath united theory and practice in many fields: from history and philosophy of science to adult education. Until now the practical application of Neurath's philosophical convictions, his innovations in museology, have not been presented coherently. Neurath's museum and exhibition work - in the Red Vienna (1925-1934) and later in the Netherlands and in the UK - had a specific educational mission and a clear commitment to its users, shaped by egalitarian notions and meant to promote social development. Nowadays, museums are searching for ways to connect more closely with their audiences. The ideas and methods of Otto Neurath, his unusual approach to museums, the emphasis on communication and learning, can be better assessed with this book. It will be of great interest to those concerned with museums and exhibitions as spaces for education and communication.