In September 1945, Radbruch published a short paper "Fünf Minuten Rechtsphilosophie" (Five Minutes of Legal Philosophy), that was influential in shaping the jurisprudence of values ("Wertungsjurisprudenz"), prevalent in the aftermath of World War II as a reaction against legal positivism. Radbruch's legal philosophy derived from Neokantianism, which assumes that a categorical cleavage exists between "is" ("sein") and "ought" ("sollen"). According to this view, "should" can never be derived from "Being." Indicative of the Heidelberg school of neokantianism to which Radbruch subscribed was that it interpolated the value-related cultural studies between the explanatory sciences (being) and philosophical teachings of values (should). In relation to the law, this triadism shows itself in the subfields of legal sociology, legal philosophy and legal dogma. Legal dogma assumes a place in between. It posits itself in opposition to positive law, as the latter depicts itself in social reality and methodologically in the objective "should-have" sense of law, which reveals itself through value-related interpretation. The core of Radbruch's legal philosophy consists of his tenets the concept of law and the idea of law. The idea of law is defined through a triad of justice, utility and certainty. Radbruch thereby had the idea of utility or usefulness spring forth from an analysis of the idea of justice. Upon this notion was based the Radbruch formula, which is still vigorously debated today. The concept of law, for Radbruch, is "nothing other than the given fact, which has the sense to serve the idea of law." Hotly disputed is the question whether Radbruch was a legal positivist before 1933 and executed an about-face in his thinking due to the advent of Nazism, or whether he continued to develop, under the impression of Nazi crimes, the relativistic values-teaching he had already been advocating before 1933. The problem of the controversy between the spirit and the letter of the law, in Germany, has been brought back to public attention due to the trials of former East German soldiers who guarded the Berlin Wall—the so-called necessity of following orders. Radbruch's theories are posited against the positivist "pure legal tenets" represented by Hans Kelsen and, to some extent, also from Georg Jellinek.