basic belief See BERKELEY, FOUNDATIONALISM,. LOGICAL POSITIVISM , PLANTING. basic norm, also called Grundnorm, in a legal system, the norm that determines the legal validity of all other norms. The content of such an ultimate norm may provide, e.g., that norms created by a legislature or by a court are legally valid. The validity of such an ultimate norm cannot be established as a matter of social fact (such as the social fact that the norm is accepted by some group within a society). Rather, the validity of the basic norm for any given legal system must be presupposed by the validity of the norms that it legitimates as laws. The idea of a basic norm is associated with the legal philosopher Hans Kelsen. See also JURISPRUDENCE , PHILOSO- PHY OF LA. M.S.M.