There is a choice of second reading; for our purposes, let’s take Revelation 21:10-14, 22-23. In this reading, the angel shows St. John the heavenly Jerusalem, the City of God, which he tells us “had twelve courses of stones as its foundation [the Greek has themelious dōdeka, “twelve foundations”], on which were inscribed the twelve names of the twelve apostles of the Lamb.” This should call back to our minds St. Paul’s words to St. Timothy, where he refers to the Church as “the pillar and foundation [hedraiōma]of the truth”.
Again with the Gospel we have our choice, so let’s follow John 14:23-29, which forms part of Jesus’ “Last Supper discourse”. In this passage, the Lord promises the gathered disciples, who will (with one lamentable exception) become his first apostles, that “The Advocate, the holy Spirit that the Father will send in my name — he will teach you everything and remind you of all that I told you.” Earlier, he had said, “And I will ask the Father, and he will give you another Advocate to be with you always, the Spirit of truth, which the world cannot accept, because it neither sees nor knows it. But you know it, because it remains with you, and will be in you” (vv. 16-17).
Let’s return briefly to the first reading: The Council came together because of trouble some Jewish Christians were causing by telling gentile Christians, “Unless you’re circumcised according to the law of Moses, you can’t be saved.” In the letter the Council writes in response, they tell the readers bluntly that the Judaizers had no authority from the Church to preach this divisive heterodoxy.
Not, “They had no warrant from Scripture.” Not, “They had no justification from what Jesus said (or didn’t say).” Rather, “They had no mandate from us, the leaders of the Church.”
Christianity was not founded on Scripture. Not even Judaism was founded on Scripture, but on promises spoken to men of old by God which are recorded in Scripture. This is not mere word-play but a matter of logical and chronological sequence — first came the actions, then came the traditions; then came the records, growing out of the traditions organically. This sequence doesn’t deny the God-inspired nature of Scripture (cf. 2 Tim 3:16), but rather sets Scripture in its right relation to the teaching authority of the Church.
In the same way, Christianity was founded on the witness of men, as St. Peter reminds us:
For we did not follow cleverly devised myths when we made known to you the power and coming of our Lord Jesus Christ, but we were eyewitnesses of his majesty. For when he received honor and glory from God the Father and the voice was borne to him by the Majestic Glory, “This is my beloved Son, with whom I am well pleased,” we heard this voice borne from heaven, for we were with him on the holy mountain. And we have the prophetic word made more sure. … First of all you must understand this, that no prophecy of scripture is a matter of one’s own interpretation, because no prophecy ever came by the impulse of man, but men moved by the Holy Spirit spoke from God (2 Pet 1:16-21).
The last line is difficult, and therefore subject to misinterpretation — just one example of why, as St. Vincent of Lérins put it, “the rule for the right understanding of the prophets and apostles should be framed in accordance with the standard of Ecclesiastical and Catholic interpretation” (Commonitory [AD 434], 2:5).
Scripture doesn’t belong to individuals but to the community of the faithful, and therefore can’t be interpreted personally but communally and corporately. Moreover, they’re not to be interpreted one way for one time and another way for another time; nor one way for Africans, a second way for Asians, a third for Europeans and yet a fourth way for Americans. Rather, “We are a body knit together as such by a common religious profession, by unity of discipline, and by the bond of a common hope” (Tertullian [AD 197], Apology 39). Thus St. Irenaeus of Lyons:
… [T]he Church, having received this preaching and this faith, although scattered throughout the whole world, yet, as if occupying but one house, carefully preserves it. She also believes these points [of doctrine] just as if she had but one soul, and one and the same heart, and she proclaims them, and teaches them, and hands them down, with perfect harmony, as if she possessed only one mouth (Against Heresies [ca. 200], 1:10:2).
Communion and community share more than a single linguistic root. They share an idea of sharing, a commonality of bonds of faith, belief and action that rise above time, place and nationality. We are a community not because we show up in the same building at the same time every week or so but because we profess the same faith as was professed in Jerusalem so long ago.
That, ultimately, is the reason for an institutional Church — for dogmas and doctrines, for ecumenical councils and papal encyclicals, for priests and bishops: to carefully preserve the faith, to proclaim and teach and hand it down with perfect harmony throughout the ages until Christ comes again. The Church, guided by the Holy Spirit as Jesus promised, is the foundation and support of our faith. She is not here to be our boss, but our teacher and mentor.
 Also translated as base, ground, bulwark and support.
 In fact, Judaism only recognizes the first five books, the Torah, as “Scripture” in the same sense that Christians use the term.
 Literally, theopneustos, “God-breathed”. Remember that St. Paul wasn’t referring to the New Testament writings but to the law and the prophets of the Old Testament; only much later were the writings of the apostles and first-generation Christians considered “Scripture”.
 That is, the prophecies of the Old Testament confirmed by the actions and life of Jesus as the Messiah they foretold.