Sciarra Colonna slapping Pope Boniface VIII in the face.
It had been the practice to speak of the spiritual and temporal powers in terms of pope and emperor, and it was long before it was realized, at least on the papal side, that the civil power, defeated as emperor, had returned to the attack with more aggressive vigour as the Monarchy and the State. The papal-imperial controversy continued, though with increasing unreality, when the pope was at Avignon, and the emperor was Louis of Bavaria, and little effort was made to adapt to the new conditions the older theory of the co-ordinate powers of Church and State, both of immediate Divine origin but differing in dignity.
The struggle between Boniface and Philip culminated in the outrage of Anagni, where Nogaret, the French lawyer, struck the aged pope. It was a brutal act, disgraceful only to the perpetrator. Unfortunately, it was followed by the migration, a few years later, of the papal court to the prison-palace of Avignon. This premature development of French absolutism was followed by years of war and anarchy; but from her misfortunes France rose up a consolidated monarchy. In England, aristocratic misrule and some forty years of intermittent civil war produced the same result. In Spain, and even in the German and Scandinavian principalities and kingdoms, different causes tended in the same direction. Thus grew up those monarchies, powerful at home jealous of foreign interference, which contributed so much to the Reformation.
(cfr. Catholic Encyclopedia: Christendom)