Positive law or a legal system as a closed logical system has its own inner coherence and this characteristic is a very important element of a system. It is important because the logical structure of norms which lead concepts and conceptions, at least in theory, is the guarantee of objectiveness or impartiality (thus ‘rule of law') of a legal system. In the second part of the nineteenth century and the first decade of the twentieth century however, legal theory was dominated by a kind of reductionism. It reduced the legal system to logical coherence. Exaggerating the logical element, it neglected other aspects of law – namely social reality and ethics. The first reactions were important but they depended completely on temporary social or judicial needs and were unsystematic. The second phase was not only a reaction but also gave birth to a new science, the sociology of law. So sociology of law has to have two opposite aspects: first, in order to prevent legal systems being withdrawn it always has to be critical and second, to help solve social problems it has to build up a strong theoretical base.