On November 9, 324 Pope Sylvester consecrated one of the first churches built by Christians once the Emperor Constantine granted them freedom to worship. This church was given special dignity and is the pope's church. It was built on one of the seven hills in Rome -- the Lateran Hill. Besides being called St. John Lateran, it is also referred to as the Mother of all the churches in Rome and of the world. It is the place where the pope has his chair, the Chair of Peter, meaning that from there the pope makes any authoritative teachings and declarations. On those infrequent occasions when an infallible statement was made, such as on the Assumption, it was from this chair in the Basilica of St. John Lateran. This feast is a sign of unity with the Pope.
The Catholic Church is not a building; this is true. But, each church building is a sign of the members of Christ's Body the Church. Each church building is an especially holy place where the Word of God is proclaimed and where bread and wine are consecrated in to the Body and Blood of Jesus Christ. We call this the Holy Eucharist and also the Blessed Sacrament which is reserved in the tabernacle of each Catholic church.
Today, we thank God that we have Catholic Church buildings, some of which are very beautiful like our own St. Michael's. We have places where we can pray quietly in the real presence of our Lord. We can also, as it were, for a time get out of the busy world to receive the Sacraments.
We are grateful to God also for the papacy. the pope is the guarantor of unity and of truth. So, we commemorate the original dedication of St. John Lateran Basilica as a sign of our gratitude.