"it was in Antioch that the disciples were first called Christians."

Then he went to Tarsus to look for Saul,
and when he had found him he brought him to Antioch.
For a whole year they met with the Church
and taught a large number of people,
and it was in Antioch that the disciples
were first called Christians.

-- Acts 11:19-26

Christians of the first centuries said, "The world was created for the sake of the Church." God created the world for the sake of communion with his divine life, a communion brought about by the "convocation" of men in Christ, and this "convocation" is the Church. The Church is the goal of all things, and God permitted such painful upheavals as the angels' fall and man's sin only as occasions and means for displaying all the power of his arm and the whole measure of the love he wanted to give the world:

Just as God's will is creation and is called "the world," so his intention is the salvation of men, and it is called "the Church."

-- CCC 760

The Tradition here in question comes from the apostles and hands on what they received from Jesus' teaching and example and what they learned from the Holy Spirit. The first generation of Christians did not yet have a written New Testament, and the New Testament itself demonstrates the process of living Tradition.

Tradition is to be distinguished from the various theological, disciplinary, liturgical or devotional traditions, born in the local churches over time. These are the particular forms, adapted to different places and times, in which the great Tradition is expressed. In the light of Tradition, these traditions can be retained, modified or even abandoned under the guidance of the Church's Magisterium.

-- CCC 83