Here's a brief excerpt from Bryan's essay (emphasis mine):
In dialoguing with a person who holds a gnostic conception of the Church, we have to show that Christ founded a visible Church. We can do this by showing that schism is impossible if the Church is not visible, and yet schism is clearly forbidden in Scripture -- cf. 1 Corinthians 1:10. Scripture also enjoins unity among Christians; that would be nonsensical if ecclesial unity were complete merely by all Christians being Christian. (Those holding a gnostic conception of the Church typically have no conception of schism, or any way of showing whether they are or are not in schism.) We can also point to Scripture passages that show the importance of church discipline (e.g. St. Matthew 18:15ff), and obedience to ecclesial authority (e.g. Hebrews 13:17). Those two things do not fit into the gnostic conception of the Church. We can also show that the Church is a living body, and that bodies are material, not invisible.I'm going to print out this essay (along with the article from This Rock that he linked to) and read them more closely. If I read something interesting online, often I'll print it out, read it again, highlighting things of interest, and filing it away in a folder on my desk (as opposed to a folder on my desktop... this is paper I'm talking about). I like that better than merely saving a digital copy in Word with highlighted portions.
Those persons who agree that Christ founded a visible Church, but deny that any present institution is it, are by that denial saying that the Church which Christ founded ceased to exist, and that Christ's promise regarding the indefectibility of the Church was false. Those persons who agree that Christ founded a visible Church, but deny that apostolicity is through sacramental succession from the Apostles, have not fully removed the gnosticism of early Protestantism from their theology.
I'm reading Mystici Corporis Christi right now, in which Pope Pius XII talks about the doctrine of the Mystical Body of Christ (the Church), and identifies some errors and misconceptions about it. Bryan's essay (and the article from This Rock) seem to be good companions to this encyclical. I'll write about it soon!
Postscript: Bryan also has a more recent post/essay on "The Incarnation and Church Unity". It's also very much worth reading!
Post-postscript: Here's the set of documents I ended up putting together in one Word document (87 K, 13pp) printing out to read:
- Is the Church Visible or Invisible? (John J. Moran for This Rock)
- Church and Jesus Are Inseparable, Says Pope (ZENIT)
- Apostolicity (Bryan Cross)
- Sacramental Apostolic Succession and Ecumenical Unity (Bryan Cross at Principium Unitatis)
- Apostolicity in Acts 15 (Bryan Cross at Principium Unitatis)
- The Incarnation and Church Unity (Bryan Cross at Principium Unitatis)
- Church and Jesus Are Inseparable, Says Pope (Bryan Cross at Principium Unitatis)