The problem of legitimacy can be approached in three different ways in the current intellectual and social conditions. The first is the modernist search for universally binding, general and neutral criteria of the system of law and political domination. Political institutions and order may be called legitimate if decision-making procedures can claim universal validity established by rational argumentation. Knowledge and humanity are universal categories with the power to legitimate political violence and law's enforcement. If law and political power are outcomes of rational argumentation, violence is transformed into a legitimate political structure. Political structures cannot be a mere social convention emerging contingently from the process of social communication. This communication must have its elaborate order corresponding to rational argumentation. Knowledge is the transcendent source of the validity of political norms and conventions.