Ignatius:
The Holy Scripture is a product of Sacred Tradition. To see how this was done, research the Canon of the New Testament.
Yes, the Catechism says the Gospel is the source of
“all saving truth and moral discipline”.
The Catechism says the whole Gospel is handed down in Sacred Tradition:
"
Through Tradition, ‘the Church, in her doctrine, life and worship, perpetuates and transmits to every generation all that she herself is, all that she believes.’ "
Thus all the apostles believed , the entire Gospel, was handed down “through Tradition”
Of course this Gospel they handed down, the source of **“all saving truth and moral discipline”, **is simply the Catholic faith.
We often think of the Gospel of only the words of Jesus in the four narratives of His life, the four Gospels. But actually the Gospel is everything the apostles handed down, in other words, the entire Catholic faith. Thus, to proclaim the Gospel, we simply proclaim the Catholic Faith. To teach the Gospel, we teach the Catholic faith.
So, when the apostles taught the Gospel, they did not do so by reading the four Gospels from beginning to end. No one could learn like that, and they don’t contain the whole Gospel. Thus the apostles had to organize what they taught. They had to first, teach the trinity, that is who God the Father was, who Jesus was, who the Holy Spirit was. They had to teach the hierarchy of truths, that is the basics of salvation history, using the scriptures, and then teach the articles of the creed, the sacraments, the commandents and prayer. In other words, the Gospel they taught was the Catholic faith. See the Directory for Catechesis for more on this.
Catehisms are simply a summary of the Gospel the apostles taught and preached.
Later the New Testament was written.
The Catechism says certain elements of this tradition were written in scripture.
#126
“The sacred authors, in writing the four Gospels,
selected certain of the many elements which had been handed on…”
Thus only parts of the Gospel were written in scripture. The whole Gospel is handed down in Tradition, of which the Catechisms are a summary of this Gospel the apostles taught and preached. In other words, as taught infallibly in the Directory for Catehesis
** Catechesis is nothing other than the process of transmitting the Gospel, as the Christian community has received it, understands it, celebrates it, lives it and communicates it in many ways. **
** In local catechisms, the Church communicates the Gospel in a manner accessible to the human person so that it may be really perceived as the “Good News” of salvation. **
