In the Middle Ages, hierocracy or papalism was a current of Latin legal and political thought that argued that the pope held supreme authority over not just spiritual, but also temporal affairs. In its full, late medieval form, hierocratic theory posited that since Christ was lord of the universe and both king and priest, and the pope was his earthly vicar, the pope must also possess both spiritual and temporal authority over everybody in the world. Papalist writers at the turn of the 14th century such as Augustinus Triumphus and Giles of Rome depicted secular government as a product of human sinfulness that originated, by necessity, in tyrannical usurpation, and could be redeemed only by submission to the superior spiritual sovereignty of the pope. At the head of the Catholic Church, responsible to no other jurisdiction except God, the pope, they argued, was the monarch of a universal kingdom whose power extended to Christians and non-Christians alike.

Henry of Segusio, usually called Hostiensis, was an Italian canonist of the thirteenth century, born at Susa (Segusio), in the ancient Diocese of Turin. He died at Lyon.