Before the priest leaves the altar, one last reading is done. This reading begins in John 1:1 and is called "The Last Gospel." The historic purpose of the reading of John 1:1-14 at the close of Mass is as a tool to combat heresy. Between the 12th and 14th centuries there was a gnostic revival and dualist heresy known as Catharism which essentially denied the divinity of Christ, amongst other beliefs. Concerning dualism, they argued for two gods, a god of the Old Testament who is evil and a god of the new testament who is good. Concerning gnosticism, they believed the evil god created all matter and the good god created all that is spirit so that all physical matter was evil and needed to be purged or cleansed in some fashion to become more spiritual or holy. Jesus could therefore not be both God and man, for in their belief system God could not have a physical body since physical matter was inherently and solely evil.
By the 13th Century, as a means of combating this heresy, the Pope decreed that the celebrants of Mass were to recite John 1:1-14 before they left the altar and returned to the sacristy. The idea was that a follower of Catharism would not be able to recite the opening verse, "in the beginning was the Word, and the Word was with God, and the Word was God," nor would a follower of Catharism be able to recite the words of the incarnation, "and the Word became flesh and dwelt among us." The act of genuflecting during this statement of the incarnation was not only an act of devotion and humility in light of the supreme humility of Jesus to take on flesh, but was also a declaration that the celebrant believed those words to be true. From these beginnings, the practice then became part of the liturgy itself so that the congregation became participants in the reading of this passage which is a vital declaration of the incarnation and divinity of Jesus.
There is a rise of pseudo-gnostic thinking and teaching within western Christianity, wherein Christ's divinity and incarnation are questioned to various degrees. Perhaps He is seen as simply a good man who had no sense of divinity; perhaps he is seen as having been declared divine rather than having been born divine. In our rationalistic culture, the tendency is to reject that which we cannot explain, and since we cannot explain the incarnation or the divinity of Christ in a comprehensive manner, these doctrines are viewed with skepticism. The reading of the Last Gospel is a benefit to the church, therefore, as it keeps the words of St. John firmly in our minds. That not only was the Word God, but the Word became flesh and dwelt among us.
In a sense, this passage of from St. John's gospel gives us our marching orders as we leave to return into the world. We carry with us the, "true light which comes into the world," and continues His mission so that others can receive Him and believe on His name. This one who is both God and Man, this one who is full of grace and truth, is the one with and of whom we have communed and is the one who we carry into the world.
(as published in St. Luke’s Sunday Bulletin, 9/30/18)