An excerpt from an article over at Called to Communion which, in passing, has a useful discussion of what it means for the Church to be apostolic:
What about the charge that Tradition is too vague to be workable? I have sometimes heard Protestants say that Tradition is of no use unless the Church can produce an exhaustive list of Traditions in the same way that she has produced an exhaustive list of inspired books. I think what motivates this objection is the belief that Scripture and Tradition must form a sort of neutral data set, from which we exegete the content of the faith. Unless I know that I have the whole set, I cannot possible draw reliable conclusions about the content of the faith.
Ironically, I think this objection works better against the Protestant doctrine of Scripture than it does against the Catholic doctrine of Tradition. On the view of someone like R.C. Sproul, we can only make a definitive account of the faith in terms of the inspired books. However, we don’t know with certainty which canonical books are inspired. (According to Sproul, we must be content with “a fallible list of infallible books.”)
Catholics, however, don’t view Scripture or Tradition this way. They do not form a neutral data set from which we independently exegete the content of the faith. Rather, they transmit the content of revelation within a community endowed with authoritative interpreters. Only within such a community could you ever know with certainty that you possessed a definitive account of the faith.
Furthermore, it is just not true to say that we don’t know the contents of Tradition. If you would know the Church’s Traditions, look to her liturgies, devotions, canons, the writings of the fathers, architecture, art, music, catechesis, and doctrinal pronouncements. Heinrich Denzinger composed a nearly exhaustive list of the latter that is widely available.1
The substantive dispute between Protestants and Catholics is not over the usefulness of Tradition, therefore, but over its authority. Does Tradition transmit the deposit of faith in a way that authoritatively conditions my interpretation of Holy Scripture and of the faith? Or, does my interpretation of Scripture stand in judgment of Tradition? We can only answer this with reference to two other questions: “What provision did Christ make for the transmission of the Christian faith? And with what authority did he invest it?”
Christ gave very specific instructions concerning the transmission of the Christian faith. First, He instituted the Church’s liturgy, and ordered that it be handed on in perpetuity. (Luke 22: 19-20; John 20: 21-23). Second, He committed His body of oral teaching, including instructions about baptism, to the disciples (the eleven), and commanded that they teach it to all nations. With this command He included a promise of divine assistance. (Matthew 28:18-20) Third, He assigned the Church the responsibility of rendering binding decisions, and promised that heaven would confirm those decisions. (Matt 16:18; 18:18)
When it comes to the apostles, we find that they transmitted each of these elements to posterity. Paul includes the elements of the liturgy as part of the deposit of faith. (1 Corinthians 11:23-24.). The elders at Jerusalem considered their disciplinary decisions to reflect the central doctrines of the faith, and to be guaranteed by the Holy Spirit. (Acts 15) And, the apostle entrusts the charge of handing on the faith to successors. Again, this charge is accompanied by the promise of divine assistance. (2 Timothy 1:6; 2 Timothy 2:2).
There is only one part of Tradition that the apostles do not mention. They completely ignore the formation of the New Testament canon. The closest they come is the reference to “Paul’s Letters” in 2 Peter 3:16, but this hardly constitutes a doctrine of the Canon. As far as we know, neither Jesus nor the apostles had any concept of a New Testament Canon serving as the primary vehicle for the transmission of the Christian faith. Anyone who says otherwise depends neither on Scripture, nor ancient Tradition, but upon modern innovation.