This book presents the theory of the validity of legal norms, aimed at the practice of law, in particular the jurisdiction of the constitutional courts. The postpositivist concept of the validity of statutory law, grounded on a critical analysis of the basic theories of legal validity elaborated up to now, is introduced. In the first part of the book a contemporary German nonpositivist conception of law developed by Ralf Dreier and Robert Alexy is analysed in order to answer the question whether the juristic concept of legal validity should include moral standards or criteria. In the second part, a postpositivist concept of legal validity and an innovative model of validity discourse, based on the juristic presumption of the validity of legal norms, are proposed. The book is a work on analytical legal theory, written from a postpositivist, detached point of view.

Virtual reality (VR) techniques are becoming increasingly popular. The use of computer modeling and visualization is no longer uncommon in the area of ergonomics and occupational health and safety. This book explains how studies conducted in a simulated virtual world are making it possible to test new solutions for designed workstations, offering a high degree of ease for introducing modifications and eliminating risk and work-related accidents. Virtual reality techniques offer a wide range of possibilities including increasing the cognitive abilities of the elderly, adapting workstations for people with disabilities and special needs, and remote control of machines using collaborative robots. Detailed discussions include: Testing protective devices, safety systems, and the numerical reconstruction of work accidents Using computer simulation in generic virtual environments On the one hand, it is a self-study book made so by well-crafted and numerous examples. On the other hand, through a detailed analysis of the virtual reality from a point of view of work safety and ergonomics and health improvement. Ewa Grabska, Jagiellonian University, Krakow, Poland Noteworthy is the broad scope and diversity of the addressed problems, ranging from training employees using VR environments with different degrees of perceived reality; training and rehabilitation of the elderly; to designing, testing, modifying, and adapting workplaces to various needs including those of disabled workers; to simulation and investigation of the cause of accidents at a workplace. Andrzej Krawiecki, Warsaw University of Technology, Warsaw, Poland

This book presents the theory of the validity of legal norms, aimed at the practice of law, in particular the jurisdiction of the constitutional courts. The postpositivist concept of the validity of statutory law, grounded on a critical analysis of the basic theories of legal validity elaborated up to now, is introduced. In the first part of the book a contemporary German nonpositivist conception of law developed by Ralf Dreier and Robert Alexy is analysed in order to answer the question whether the juristic concept of legal validity should include moral standards or criteria. In the second part, a postpositivist concept of legal validity and an innovative model of validity discourse, based on the juristic presumption of the validity of legal norms, are proposed. The book is a work on analytical legal theory, written from a postpositivist, detached point of view.