Robert Alexy born in 1945 in Oldenburg (Germany), studied law and philosophy at the University of Göttingen. His doctoral thesis, soon published, is on Theory of legal argumentation (1978), and his habilitation work, on Theory of fundamental rights (1984); Both texts have been translated, in addition to Spanish, into many other languages. Since 1986 he teaches at the University of Kiel as Professor of Public Law and Philosophy of Law. He is a member of the Academy of Sciences of Göttingen and doctor honoris causa by numerous universities (among them, those of Alicante, Buenos Aires, Tucumán, Coimbra or Rosario, in Bogota). Among his countless works are the concept and validity of law (1992, 5th edition in 2011) and compilations such as The concept and nature of law (2008) or The construction of fundamental rights (2010), in addition to the Tests contained in this volume.