"For books to be read are not so profitable for me as the living voice that even until the present day resounds on the lips of their authors." -Papias
This statement was quoted to me as an argument for the validity of the Roman Catholic doctrine of Sacred Tradition. Sacred Tradition is what Catholics believe is the second stream of Divine revelation.
From the Official Catechism:
"And [Holy] Tradition transmits in its entirety the Word of God which has been entrusted to the apostles by Christ the Lord and the Holy Spirit. It transmits it to the successors of the apostles so that, enlightened by the Spirit of truth, they may faithfully preserve, expound and spread it abroad by their preaching."
Thus, if the Magisterium says that Sacred Tradition holds to the perpetual virginity of Mary, then it must be believed, because it bears the same authority as the written Word of God.
Here is what Bauckham says in his book "Jesus and the Eyewitnesses".
Once again, we should notice a key implication of Papias' words; he does not regard the Gospel traditions as having by this date long lost a living connection with the eyewitnesses who originated them. Whether these eyewitnesses were still living would not matter if the oral tradition were essentially independent of them. Papias assumes that the value of oral traditions depends on their derivation from still living witnesses who are still living witnesses who are still themselves repeating their testimony. Now that these are few, second hand reports of what eyewitnesses now dead used to say are valuable, but Papias' whole statement implies that the value of oral tradition decreases with distance from the personal testimony of the eyewitnesses themselves.(Bauckham, p.29)