Frederick II, Holy Roman Emperor, also called Stupor mundi (Wonder of the world), was a notable European ruler who left a controversial political and cultural legacy. Considered by some to be "the most brilliant of medieval German monarchs, and probably of all medieval rulers" and admired for his multifaceted activities in the fields of government building, legislative work, cultural patronage and science, he has also been criticized for his cruelty, his neglect of Germany in favour of his Sicilian businesses. In Italy, the emperor has gained a split image, with one element being favoured over the other depending on the era and the region: tyrant, heretic, enlightened despot, Puer Apulia (boy from Apulia), Father of the Fatherland. Modern scholars generally praise the emperor's many talents, but the degree Frederick's actions and attitude can be considered to be a break from contemporary norms, as well as his contribution to contemporary advancement of knowledge (in the context of Sicilian and Hohenstaufen legacies as well as cultural developments by other courts) is often subject to debates.
Historiography
German and English accounts
Ernst Kantorowicz's biography, Frederick the Second, original published in 1927, is a very influential work in the historiography of the emperor. Kantorowicz praises Frederick as a genius, who created the "first western bureaucracy", an "intellectual order within the state" that acted like "an effective weapon in his fight with the Church—bound together from its birth by sacred ties in the priestly-Christian spirit of the age, and uplifted to the triumphant cult of the Deity Justitia." Kantorowicz's writings about Frederick were abused during the Nazi period for propaganda purpose. Joseph Mali and Yôsef Malî argue that Frederick II were not important for the Nazis the way Frederick Barbarossa or Karl the Great, as exemplars of pure Aryanness, were though. They also note that while Kantorowicz endorsed Burckhardt's thinking, that Frederick was the prototypical modern ruler, whose Gewaltstaat later became the model of tyrannies for all Renaissance princes, Kantorowicz primarily saw Frederick as the last and greatest Christian emperor, who embraced "Medieval World Unity".
Thomas Curtis Van Cleve's 1972 The Emperor Frederick II of Hohenstaufen, Immutator Mundi also acknowledges the emperor's genius, as a ruler, lawgiver and also as a scientist. Karl Leyser opines that Kantorowicz and Cleve as well as other historians are too hagiographic. Leyser writes that Frederick was an individual with many gifts, but was "neither likeable nor reassuring", with a personality damaged greatly during his terrible childhood. Leyser also points out that Cleve exaggerates the role of Frederick's court in the transmission of Aristotelean and Arabic knowledge to Western court: Frederick's court was important but did not play the leading role, let alone monopolizing this process.
In 1992, David Abulafia wrote a revisionist work which argues that Frederick was not a rationalist or an early free-thinker, but a medieval ruler concerned with dynastic goals and also a "victim of his dual inheritance", who was forced to act in his own defense in front of popes who were determined to destroy his power. Regarding his cultural activities, Abulafia opines that "Frederick's cultural patronage was a pale shadow of that of his Norman ancestors" and that his reign marked "the end, not the revival, of convivencia in his southern kingdom."
Dorothea Weltecke notes that despite Abulafia's effort to destroy what he saw as German mystification of a "medieval emperor", most historians today still see Frederick as a man who transcended his time and shared our values of secularism, tolerance and rationalism. Weltecke opines that Frederick's diverse style of ruling in his different lands and his ability to adapt make it difficult to present in a coherent manner his politics, let alone his personality, that in his time, already provoked either "profound adoration or vehement rejection". Regarding his role in Arabic-Christian transfer of knowledge though, Weltecke writes that the Medieval Christian culture was not a monolithic entity unanimously hostile to Muslims, thus it was not necessary for Frederick to possess a hybrid personality to be the competent diplomat and promoter of science he was. Other forces in Latin states sought Muslim cooperation against Frederick, while other religious and secular figures like Alfonso IX of León also played a role in the emergence of universities and the transfer of knowledge from the Islamic world.