In dealing with the schismatic, heretical Eastern Church, however, all careful reserve vanished and without fear or caution the Roman Pontiffs assert their prerogatives in a clear, decisive, and peremptory tone. In the Photian schism at Constantinople, Nicholas I. assumed the right to decide which of the two claimants to the patriarchate was legitimate. To Photius, who had secured the office by imperial aid, the Roman pontiff wrote a letter which up to that time was unsurpassed for supreme papal arrogance: Our Lord and Saviour . . . established the foundations of his church upon the Rock Peter. . . . Now upon this foundation the appointed builders have from time to time heaped many precious stones, till by this unwearied diligence the whole building has been perfected into indissoluble solidity. . . . Since this church of Peter is the head of all churches, it is imperative upon all to adopt her as their model in every matter of ecclesiastical expediency and institution. . . . From her all synods and all councils derive their power to bind and to loose.[343:3] The pontificate of Nicholas I., who died in 867, marks the acme of papal power during this period. The history of the Western Church, controlled by Rome, during the latter part of the ninth and the tenth century, covers a period of unparalleled corruption and debility--"a death-sleep of moral and spiritual exhaustion." The Papacy as a constructive spiritual force almost disappears from view. The lofty ideas of Leo I., Gregory I., and Nicholas I.--their magnificent ambitions for the Church, their imperial rule, and their commanding, aggressive spirit--all disappeared. The causes may be found in weak, wicked, worldly Popes, in anarchy and political confusion in Italy, and in feudalism. The Church was reaping the reward of a close alliance with the state. All the gains made by the Church during this epoch were of a secular character. The moral and spiritual powers of Latin Christianity lay dormant beneath a mass of corruption, self-seeking, and worldly passions which covered them and nearly extinguished them. The marvellous vitality of the organisation of the Church alone saved her from disintegration in that period of decentralisation. The spirit of the Pseudo-Isidorian Decretals, from this standpoint, had become the saviour of the Church. The next force that appeared in western Europe to rescue the Church from the low state of spiritual degeneration to which she had fallen was, strange to say, the Holy Roman Empire under the guidance of another mighty German ruler. SOURCES A.--PRIMARY: 1.--Roberts and Donaldson, _Ante-Nicene Christian Library_, ix., pt. 2, p. 144 _ff._ Has letters of six Popes. 2.--Schaff, _Ante-Nicene Fathers_, viii., 601. 3.--Henderson, _Select Historical Documents of the Middle Ages_, 319. Contains the Donation of Constantine.