In 1261 Michael Palaeologus, the Greek Emperor of Nicea, conquered Constantinople, and thus put an end to the Latin Empire established by the Fourth Crusade. But the wily Greek feared a general movement in Latin Christendom to recover the city from him, and to gain time by diplomacy he opened negotiations for the reconciliation of Eastern and Western Christendom with Urban IV., then newly chosen to the papacy. The Pope summoned Thomas Aquinas from Paris to Rome, to aid in these negotiations by his erudition and acuteness. The subject was one into which his previous studies had not conducted him, but a scholastic philosopher must be prepared to write on any topic. _De omni scibili_ was his scope. So Thomas wrote his _Treatise against the Errors of the Greeks_ (_Opusculum contra Errores Graecorum_) by the papal order. In its preparation he became at once the victim and the instrument of one of the most memorable forgeries in ecclesiastical literature. The Dominicans had followed the Latin Empire into the East, but found themselves at a loss for authorities to prove to the Greeks that the autocratic papacy was a venerable, much less a primitive institution, of the Christian Church. One of them conceived the bright thought of manufacturing a supply. So he sent to Urban IV. a long _catena_ of quotations from the Greek fathers, especially the two Cyrils and the Council of Chalcedon, in which the papal authority and infallibility were set forth with a boldness never used even in the West. The Pope fully believed in their genuineness and handed them over to Thomas, who incorporated many of them into his _opusculum_, besides using them in his greater work. He knew too much about the teachings of the Greek fathers not to be staggered by the quotations as to the Procession of the Holy Spirit from the Father and the Son, and he expressed his doubts in a letter to Urban. But he was not staggered by the forger’s showing that the Greeks accepted the universal jurisdiction and infallible authority of the papacy. In this way the notion of a universal episcopate and an infallibility in the Bishop of Rome, from being the audacious whim of a few canonists, passed into the dogmatic theology of the Church, and came to be made an article of faith in our own time. (See Acton-Döllinger-Huber’s book, _Janus, or the Pope and the Council_, chap, iii., section 18.)