Sacred Tradition is the Mother of the Bible
It's still a jolt for some people to realize this, but the Bible did not fall down out of the sky, leather-bound and gold-monogrammed with the words of Christ in red, in AD 95. Rather the canon of Christian Scripture slowly developed over a period of about 1500 years. That does not mean, of course, that Scripture was being written for 1500 years after the life of Christ. Rather, it means that it took the Church some fifteen centuries to formally and definitively state which books out of the great mass of early Christian and pseudo-Christian books constituted the Bible.
The process of defining the canon of Scripture is an example of what the Church calls "development of doctrine". This is a different thing than "innovation of doctrine". Doctrine develops as a baby develops into a man, not as a baby grows extra noses, eyes, and hands. An innovation of doctrine would be if the Church declared something flatly contrary to all previous teaching ("Pope John Paul Ringo I Declares the Doctrine of the Trinity to No Longer Be the Teaching of the Church: Bishop Celebrate by Playing Tiddly Winks with So-Called 'Blessed Sacrament'"). It is against such flat reversals of Christian teaching that the promise of the Spirit to guard the apostolic Tradition stands. And, in fact, there has never ever been a time when the Church has reversed its dogmatic teaching. (Prudential and disciplinary changes are another matter. The Church is not eternally wedded to, for instance, unmarried priests, as the wife of St. Peter can tell you.)
But though innovations in doctrine are not possible, developments of doctrine occur all the time and these tend to apply old teaching to new situations or to more completely articulate ancient teaching that has not been fully fleshed out. So, for example, in our own day the Church teaches against the evils of embryonic stem cell research even though the New Testament has nothing to say on the matter. Yet nobody in his five wits claims that the present Church "invented" opposition to embryonic stem cell research from thin air. We all understand that the Church, by the very nature of its Tradition, has said "You shall not kill" for 2,000 years. It merely took the folly of modern embryonic stem cell research to cause the Church to apply its Tradition to this concrete situation and declare what it has always believed.
Very well then, as with attacks on sacred human life in the 21st century, so with attacks on Sacred Tradition in the previous twenty. Jesus establishes the Tradition that he has not come to abolish the Law and the Prophets but to fulfill them (Mt 5:17). But when Tradition bumps into the theories of early Jewish Christians that all Gentiles must be circumcised in order to become Christians, the Council of Jerusalem (Acts 15) is still necessary to authoritatively flesh that Tradition out. Moreover, the Council settles the question by calling the Bible, not to the judge's bench, but to the witness stand. Scripture bears witness to the call of the Gentiles, but the final judgment depends on the authority of Christ speaking through his apostles and elders whose inspired declaration is not "The Bible says..." but "It seemed good to the Holy Spirit and to us..." (Acts 15:28).
In all this, the Church, as ever, inseparably unites Scripture as the light and Sacred Tradition as the lens through which it is focused. In this way the mustard seed of the Kingdom continues to grow in that light, getting more mustardy, not less.
How then did Tradition develop with respect to the canon of Scripture?
On that, more next time.