I will take you for my people, and I will be your God -Exodus 6:7
[Picture from The Library of Congress depicting the Merchant, the Friar, the Monk, the Franklin, the Wife of Bath, the Parson, and the Ploughman, all from Chaucer's Canterbury Tales.]
Perhaps some of you have heard of "Evangelicals on the Canterbury Trail." These are Evangelicals who by a taste for Liturgy and by the providence of God begin moving backward to Catholicism. Evangelicalism came into existence when The Anglican Whitfield began The Great Awakening (1740s) in the American Colonies. These Anglicans had come from England, and had broken from The Catholic Church in 1534. Thus it is, that by Evangelicals going on pilgrimage to Canterbury that many have found their way back to Rome.
The OCSP exists for people like this. They have discovered a notion of The Church as The People of God through Liturgy and Pilgrimage. One will find both of these in the Vatican II document Lumen Gentium: The Dogmatic Constitution on The Church.
The Church as The People of God, not "the peoples"
A "People" is singular, not plural. So, "What is The Church?" The People of God. Peoples can have nothing in common, but a People are specifically a group that has something in common. The Church's members are many, but it is one People. It has a culture, a language, initiation rites, a mission, and so forth. It consists of three Orders: Ecclesial, Civil, and Familial - in that order.
The People of God is a Priesthood and not just "The People"
Though they differ from one another in essence and not only in degree, the common priesthood of the faithful and the ministerial or hierarchical priesthood are nonetheless interrelated: each of them in its own special way is a participation in the one priesthood of Christ.
-Lumen Gentium: Dogmatic Constitution on The Church
I. The Common Priesthood: what we all share in in virtue of our Baptism as part of the one Christ
II. Ministerial/Hierarchical Priesthood: the intercessor who acts in the Person of Christ during Mass
The desire to say The Catholic Church is evolving to become more democratic by making everyone a priest is thus wrong. But it is also unfitting to say "The Clergy and The People of God" as if the clergy are not part of The People of God. This would no doubt create strife between laity and clergy. Pope Benedict XVI suggests this is exactly what happened by misreading Vatican II as early as 1973:
After the Council, the expression was taken up enthusiastically, but in a way that neither Ratzinger nor the Council Fathers had intended. Suddenly it became a slogan: "We are the People!" The idea of a "Church from below" developed; its proponents wanted to engage in polemics against those who held office and to carry out their agenda by democratic majority vote. Although the theological, biblical concept of people was still the idea of a natural hierarchy, of a great family, suddenly it was reinterpreted in a Marxist sense, in which "people" is always considered the antithesis to the ruling classes. The centre of the Christian faith, however, can only be God's revelation, which cannot be put to a ballot. Church is being called by God. Joseph Ratzinger said: 'The crisis concerning the Church, as it is reflected in the crisis concerning the concept "People of God", is a "crisis about God"; it is the result of leaving out what is most essential [ie God]. -My Brother The Pope, George Ratzinger
Many of our Protestant brethren take a similar position since they think there's nothing divine to The Church. It's just "we the people" in "our community." This can very well be Marxist. Like Paul, you can argue in Evangelization, after you listen to their position first. The essential problem with this the idea that The Church is nothing more than "The People" is that Jesus said to Peter, "on this rock I will build my church" (Mt. 18:16). That means it has a divine source. It's also identified as the body of Christ, who is divine (Eph 1). Thus it is divine. It is more than The People.
How Martin Luther spread the idea "Each of us is a priest" and why this is incorrect
Martin Luther popularized the idea that Baptism makes each of us a priest. This is one reason why many of our Protestant brethren don't even pretend to have priests; they think it redundant to Baptism or a profession of faith. Once you accept each of us is a priest, it's not long till you throw out the priesthood altogether.
In fact, we are all consecrated priests through Baptism, as St. Peter in 1 Peter 2 says, "You are a royal priesthood and a priestly kingdom," and Revelation, "Through your blood you have made us into priests and kings." -Martin Luther, Weimar Ausgabe, vol. 6
The "You" in "You are a royal priesthood" is actually 2nd person plural, and priesthood is singular. A better rendered in Southern it reads, "Y'all are a royal priesthood." This would be like saying, "Y'all are a great team" then concluding each player was a team.
"You have made us into priests and kings," (Rev 5:9) might mean each of us is a priest, or not. If our baseball team said, "Coach, you have made us in-fielders and out-fielders," does that mean each of us in an in-fielder and an out-fielder? Not necessarily, because we're speaking of the team, not about individuals. So we ought read The Scriptures with The People of God in mind, not just ourselves as individuals. E.g. "Before I formed you in the womb I knew you" may be about Jeremiah as a foreshadow to Christ, and not so much about me.
The People of God on Pilgrimage
The prototypical story of The People of God is Moses with the Israelites in Exodus. The primary story though is Jesus and his disciples forming one whole Christ in the Gospels and Acts of the Apostles. We are the long trail of God's People draped across the mountainsides, snaking up the hills, piling through time and rivers, bursting forth onto greener pastures throughout the world. We venture out, make mistakes, and hopefully grow in wisdom along the adventure.
Protestants are our brethren who lost the way, forgot they were part of a caravan full of friends and family. Sometimes they were born into that reality and have no way of knowing that's even what they're supposed to be a part of. Invite them back to the adventure of The Catholic Church, and help them see the end of their journey is with a people, not alone. Pilgrims to this day invite others to walk with them, and so too we should.
And remember, The Canterbury Trail ends at Canterbury Cathedral. St. Thomas Becket's shrine is a testament to The Catholic Church defying illegitimate authority used by the State to defy The Church's rights. People went on that pilgrimage to pray that St. Thomas Becket might pray for them. It is not Anglicanism that the shrine is a testament to, it's Catholicism. Though the Henry Kings wished for a state religion they could use as a puppet, St. Becket defied them in the name of Christ and his Church. That's what the pilgrimage is about, that Christ's Kingdom is not of this world, though it's in it. The People of God know this is part of coming to be in the World but not of it.
The People of God as The Human Aspect of The Church