'validity' (not to be confused with logical validity), which is that the creation of the lower norm has been authorised by the higher norm. Since this moment of creation always involves extraneous considerations, Kelsen does not need to supplement his model with a concept of 'discretion'. What has to be consistent in a dynamic order of norms is only the process of authorising. This process can (and perhaps always does) result in multiple and mutually uneven strands of hierarchy, such as legislative, executive and judicial strands. In each strand, at every point in the process of norm-creation, many types of extra-legal factor may be taken into account—moral, political, economic and others. Kelsen notes that, in this respect, the Pure Theory of Law has an affinity with American 'legal realism'. At the same time, the 'hierarchy' model does not readily fit a common-law system. It takes as its paradigm a single constitutional document under which codes and statutes are enacted, with both administration and adjudication in subordinate places. However, at least outside the United States, common-law systems are moving in the direction of that paradigm. The 'hierarchy' model also fits public law more readily than private law. It is difficult to be convinced by Kelsen's contention that, in private transactions, the parties are exercising legal authorisation. Basic norm (Grundnorm) Kelsen assumes, however, that the scientific representation of a positive-legal order, as a hierarchy of legal propositions, must have a guarantor of unity. This guarantor cannot be other than a component of the representation, hence a legal proposition. Being a legal proposition, it counts as a representation of an actual norm. So Kelsen calls it, elliptically, a 'basic norm (Grundnorm)'. Notes Sources Further reading Selected works by Kelsen Reine Rechtslehre, Vienna 1934. Introduction to the Problems of Legal Theory (1934; Litschewski Paulson and Paulson trans.), Oxford 1992; the translators have adopted the subtitle of the first edition, Einleitung in die rechtswissenschaftliche Problematik, in order to avoid confusion with the English translation of the second edition. 'On the Theory of Interpretation' (1934; Litschewski Paulson and Paulson trans.) (1990) 10 Legal Studies 127. Law and Peace in International Relations, Cambridge (Mass.) 1942, Union (N.J.) 1997. Peace Through Law, Chapel Hill 1944, Union (N.J.) 2000. Reine Rechtslehre, Vienna 1960, "2nd edn" although a different work; amended, Tübingen 2017. Pure Theory of Law (1960; Knight trans.), Berkeley 1967, Union (N.J.) 2002. Théorie pure du droit (1960;