The pure theory describes the positive law as an objectively valid order and states that this interpretation is possible only under the condition that a basic norm is presupposed the pure theory thereby characterizes this interpretation as possible not necessary and presents the objective validity of positive law only as conditional namely conditioned by the presupposed basic norm pt2 217 218. Pure theory of law german reine rechtslehre is a book by legal theorist hans kelsen first published in 1934 and in a greatly expanded second edition effectively a new book in 1960the second edition appeared in english translation in 1967 as pure theory of law the first edition in english translation in 1992 as introduction to the problems of legal theory. Pure theory of law is concerned only with that part of knowledge that deals with law and does not include anything which does not belong to law as subject matter and therefore it frees the science of law from the foreign elements according to this theory of law the science of law includes legal norms and does not recognise natural realities. Kelsens pure theory of law hla harts theory premises kelsen started his pure theory with certain premises he believed that a theory of law must always be the basic norm grundnorm kelsen distinguished between legal science and natural science on the basis of oughts hla harts