I was reading a piece on Catholic apologetics, and it said that the Catholic Church was a visible church with marks. Can you explain what this implies?
First and foremost, The typical Protestant conception of the Church is that it is invisible. Though individuals may group together for fellowship and Bible study, their churches are really like clubs in a city. The real church, say Protestants, is the broad and unseen group of the saved.
The Catholic Church, in contrast, admonishes that the Church is a visible organization. Being a visible organization, it can be identified–it has marks. The marks are that it is one, holy, catholic, and apostolic–“one” in that it is a united organization, “holy” in that it is an organization divinely established, “catholic” in that it is to embrace all of mankind, and “apostolic” in that a line of succession has been kept with the power Christ passed to Peter and the apostles.