This book is a scientific basis for understanding the urgent need for a Great Transformation to a third step in social evolution. Already being a community of common destiny, humanity can form an actual unity through diversity to avoid extinction. Social actors can recognise informational imperatives for cognition, communication and co-operation to achieve such a unity. By doing so, they apply a logic that underlies the structuration of any agency, which is a real logic of self-organising systems from the physical to the social. This logic is the Logic of the Third - the Third is a meta-structure that emerges in a leap. The agents interact and when they co-act they are likely to form a real meta-structure of organisational relations. Informational agents anticipate this by generating requisite information in their attempt to cope with complex challenges. Such an information is a meta-structure too. The Third helps achieve synergy effects. This book discusses considerations from philosophy, systems theory, the study of information, social systems, social information, ecology and technology. It addresses ethical issues connected with the long-forgotten arms race in an atomic age, the global warming not yet under control, the pandemic misunderstood, the social question still unanswered.