This revised and expanded second edition features a new analysis of the analogies and the differences between the error/uncertainty-related approach adopted in physical measurement and the validity-related approach adopted in psychosocial measurement. In addition, it provides a better analysis and presentation of measurement scales, in particular about their relations with quantity units, and introduces the measurand identification/definition as a part of the "Hexagon Framework" along with new examples from the physical and psychosocial sciences. Researchers and academics across a wide range of disciplines including biological, physical, social, and behavioral scientists, as well as specialists in measurement and philosophy appreciate the work¿s fresh and provocative approach to the field at a time when sound measurements of complex scientific systems are increasingly essential to solving critical global problems.