We lay down this for ever, that neither the bishops of Gaul nor those of any other province shall attempt anything contrary to ancient usage, without the authority of the venerable man, the Pope of the Eternal City. Even in the height of this quarrel other provinces were not neglected, as a few letters of the year 447 amply show. The letter to the Spanish Bishop Turribius of Astorga[56] is notable as the first explicit Papal approval of the execution of a heretic. It is usual to point out that the errors of Priscillian, the heretic in question, were believed to include magical practices (then a legal and social crime) as well as Manichæan and Gnostic tenets. But we must recognize one of the most terrible principles of the Middle Ages, and something far more than social zeal, in the following words of Leo: Although ecclesiastical mildness shrinks from blood-punishments, yet it is aided by the severe decrees of Christian princes, since they who fear corporal suffering will have recourse to spiritual remedies. Here is no reference to legal or social crimes, but to an error which concerns the ecclesiastic. Similar letters, enforcing discipline in the accents of an undisputed head of the Church, were sent to the bishops of Sicily,[57] the bishop of Beneventum,[58] and the bishop of Aquileia. These quotations from the letters and sermons of Leo will suffice, not only to show the untiring energy and lofty aim of the man, but to convince us that the primacy of Rome in the West is now won. West of the Adriatic, St. Hilary is the last great rebel against the Roman conception. It is true that this spiritual supremacy is still, in part, reliant on "the severe decrees of Christian princes," but the imperial authority is fast fading into nothing, and in another generation the Papal autocracy will stand alone. Leo was not ambitious. Something of the instinctive masterliness of the older Roman may be detected in his actions, but he was a profoundly religious man, seeking neither wealth nor honours of earth, convinced at once that he discharged a divine duty and exerted an authority of the most beneficent value to that disordered Christendom. The calamities of Europe had changed the empty glories of a Damasus into a power second only to that of Octavian. When we turn to the East we have not only a most valuable indication of the evolution of Christendom into two independent and hostile Churches, but an even more interesting revelation of subtle and unexpected shades in the character of Leo. The great Pope, aided by the very calamities of the time, fastens his primacy on Europe; and, with even mightier exertions and the most tense use of all his resources, he proves that an extension of that primacy to the East is for ever impossible.