Leo wrote these Christmas sermons in the years 440-444 and 450- 454. As he states in Serm. 28.4, ". . . practically no one has gone astray who did not disbelieve the reality of two natures in Christ while at the same time acknowledging a single Person." Consequently, from the very first years of his pontificate, he emphasized--in the discharge of his episcopal duty to preach--the reality and the wonder of (in short, the "Good News" about) the Incarnation of the Word. One phase of his preaching stresses the key points of the different heresies that had broken out in various parts of the world.1. Instruction was vital if his flock was to recognize and avoid the deadly errors.
Teachers from East and West were spreading false ideas regarding the Church's doctrine about Christ. These ideas were due, in some measure, to differences in language. Even in the same language, one word could have different meanings for different people.2. In his explanations of doctrine, Leo shows himself to be a master of delineation, discernment, and clarity. His statements about the divine and the human natures in Christ are repeated over and over, in almost every possible way, and from every angle: e.g., "Remaining what he was and taking on what he was not . . ." ( Serm. 21.2); "As a result, so strong a bond of unity has been made between the two natures that, though each retains its own proper characteristics, whatever belongs to God cannot be separated from the man, while whatever belongs to the man cannot be disjoined from the divinity" ( Serm. 28.1).
Not a speculative theologian, Leo did not intend to teach anything new, but simply to preserve ". . . the Christ of the Gospels and the Apostolic Age for the faith of posterity . . .,"3. all the while realizing that ". . . the Birth of our Lord Jesus Christ exceeds all understanding and goes beyond any precedent" ( Serm. 30.4).
Another aspect of Leo's Christmas instruction stems from his endeavor to highlight for his people the joy attendant on this "Good News": ". . . our lowliness realizes how great a value its Creator has placed upon it . . ." ( Serm. 24.2); "Peace was the first thing proclaimed by the angelic choir at the Lord's Nativity. It is peace which gives birth____________________