At the time of the reign of Frederick I (1152-1190), the imperial idea had already reached maturity. Its continuity was emphasized in Europe from the Roman times, through the Carolingian Empire link. In fact, Frederick I spoke about Charlemagne as the model of emperors and had him canonized in 1165 without the requirements. The thesis on the public sovereignty that Roman law (rediscovered by the European jurists and politicians in the twelfth century) contains were also used in favor of the imperial ideas. It was of them that it was deduced the unicity and the universal character of the Holy Roman Empire, considered "a project of worldwide dominion" that symbolizes the whole period. Given these premises, it was believed in the court of Frederick I that the Empire, established directly by d