Ralf Poscher is director at the Institute for Staatswissenschaft and Philosophy of Law at the University of Freiburg, Germany. His research focuses on constitutional law, national security law and legal theory. He received his Ph.D. in law and his habilitation in public law and legal philosophy at the Humboldt-University Berlin. After holding a chair for public law, legal sociology and philosophy of law at the Ruhr University Bochum he joined the Law Faculty in Freiburg. For the academic year of 2007-2008 he was a member of the School of Social Sciences at the Institute of Advanced Study in Princeton. During his time as a visitor to the LAPA-program in spring 2012 he focuses on research for a book on theories of adjudication. The book project is part of a larger interdisciplinary research agenda “Dealing reasonably with blurred boundaries” supported by a research grant from the Volkswagen-Foundation in its program “Key Issues in the Humanities”. The theoretical aim is to identify and systematize phenomena of vagueness and indeterminacy in different fields of study with philosophy and law as the central disciplines. The practical aim is to develop and implement procedures of dealing reasonably with blurred boundaries in fields of reference like national security, environmental protection and health.