Leo to Proterius, bishop of Alexandria.
Your letter, beloved, which our brother and fellow-bishop Nestorius duly brought us, has caused me great joy. For it was seemly that such an epistle should be sent by the head of the church of Alexandria to the Apostolic See, as showed that the Egyptians had from the first learnt from the teaching of the most blessed Apostle Peter through his blessed disciple Mark1 , that which it is agreed the Romans have believed, that beside the Lord Jesus Christ "there is no other name given to men under heaven, in which they must be saved2 ." But because "all men have not faith3 " and the crafty Tempter never delights so much in wounding the hearts of men as when he can poison their unwary minds with errors that are opposed to Gospel Truth, we must strive by the mighty teaching of the Holy Ghost to prevent Christian know ledge from being perverted by the devil's falsehoods. And against this danger it behoves the rulers of the churches especially to guard and to avert from the minds of simple folk lies which are coloured by a certain show of truth4 . "For narrow and steep is the way which leads to life5 ." And they seek to entrap men not so much by watching their actions as by nice distinctions of meaning, corrupting the force of sentences by some very slight addition or alteration, whereby sometimes a statement, which made for salvation, by a subtle change is turned to destruction. But since the Apostle says, "there must be heresies, that they which are approved may be made manifest among you6 ," it tends to tile progress of the whole Church, that, whenever wickedness reveals itself in setting forth wrong opinions, the things which are harmful be not concealed, and that what will inevitably end in ruin may not injure the innocence of others. Wherefore they must put down. their blind wanderings and downfalls to themselves, who with rash obstinacy prefer to glory: in their shame than to accept the offered remedy. You do right, brother, to be displeased at their stubbornness, and we commend. you for holding fast that teaching which has; come down to us from the blessed Apostles and the holy Fathers.
For there is no new preaching in the letter which I wrote in reply to Flavian of holy memory, when be consulted me about the Incarnation of our Lord Jesus Christ; for in nothing did I depart from that rule of Faith which was outspokenly maintained by your ancestors and ours. And if Dioscorus had been willing to follow and imitate them, he would have abided in the Body of Christ, having in the works of Athanasius7 of blessed memory the materials for instruction, and in the discourses of Theophilus8 and Cyril9 of holy remembrance the means rather of praise-worthily opposing the already condemned dogma than of choosing to consort with Eutyches in his blasphemy. This therefore, beloved brother, I advise in my anxiety for our common Faith that, because the enemies of Christ's cross lie in watch for all our words and syllables, we give them not the slightest occasion for falsely asserting that we agree with the Nestorian doctrine. And you must so diligently exhort the laity and clergy and all the brotherhood to advance in the Faith as to show that you teach nothing new but instil into all men's breasts those things, which the Fathers of revered memory have with harmony of statement taught, and with which in all things our epistle agrees. And this must be shown not only by your words but also by the actually reading aloud of previous statements, that God's people may know that what the Fathers received from their predecessors and handed on to their descendants, is still instilled into them in the present day. And to this end, when the statements of the aforesaid priests have first been read, then lastly let my writings also be recited, that the ears of the faithful may attest that we preach nothing else than what we received from our forefathers. And because their understandings are but little practised in discerning these things, let them at least learn from the letters of the Fathers, how ancient this evil is, which is now condemned by us in Nestorius as well as in Eutyches, who have both been ashamed to preach the gospel of Christ according to the Lord's own teaching.
Accordingly, both in the rule of Faith and in the observance of discipline, let the standard of antiquity be maintained throughout, and do thou, beloved, display the firmness of a prudent ruler, that the church of Alexandria may get the benefit of my earnest resistance to the unprincipled ambition of certain people in maintaining its ancient privileges, and of my determination that all metropolitans should retain their dignity undiminished, as you will ascertain from the tenor of my letters, which I have addressed, whether to the holy Synod or to the most Christian Emperor, or to the Bishop of Constantinople; for you will perceive that I have made it my special care to allow no deviation from the rule of Faith in the Lord-churches, nor any diminution of their privileges through any individual's unscrupulousness. And as this is so, hold fast, brother, to the custom of your predecessors, and keep due authority over your comprovincial bishops, who by ancient constitution are subject to the See of Alexandria; so that they resist not ecclesiastical usage, and refuse not to meet together under your presidency, either at fixed times or when any reasonable cause demands it: and that if anything has to be discussed in a general meeting which will be to the benefit of the Church, when the brethren have thus met together, they may unanimously come to some resolution thereupon. For there is nothing which ought to recall them from this obedience, seeing that both for faith and conduct we have such good knowledge of you, brother, that we will not allow you to lose any of your predecessor's authority, nor to be slighted with impunity. Dated March 10th, in the consulship of the illustrious Aetius and Studius (454).