What is a church?  Allow me in this post to introduce you to three phrases:

esse notae ecclesiae (essential marks of the church)

bene notae ecclesiae (good marks of the church)

plene notae ecclesiae (full marks of the church)

My thesis is that there are substantive differences along the ecclesiological spectrum regarding the first category–the esse notae ecclesiae (essential marks of the church) but that there is ecumenical potential–that is their possibility for broad consensus–around the second and third categories.

All Christians believe that a church should be "one holy catholic and apostolic" as the Nicene Creed says.  All Christians believe a community needs a few "essential marks of the church" (esse notae ecclesiae) to be "a church."  Roman Catholics and Eastern Orthodox require structural identification with what they perceive to be "the Church" that traces its identity back to the apostles through apostolic succession.  The Reformers are famous for calling for two marks: "the Gospel is rightly taught and the Sacraments are rightly administered."  Others suggest "a church" is any group that gathers in the name of Jesus:  "For where two or three come together in my name, there am I with them" (Matthew 18:20).  

I have made a list below of lots of theologians and I have guessed where they might fall on the ecclesiological spectrum.  The ones at the top would have more formal requirements for what constitutes "a church."  The ones at the bottom would consider a community to be "a church" with relatively few formal requirements. 

All believe that their version of formal requirements and flexibility best conform to the New Testament parameters.  The ones at the bottom of the list with fewer formal requirements might say that their churches are actually "stricter" in some respects.  Thus, I labeled the list "high church" to "low church" not "very strict" to "less strict."

Though these theologians would disagree strongly about what is essential, they would all agree that "a church" should grow closer to what it is supposed to be–developing more bene notae ecclesiae (good marks of the church) and they all aspire to have the plene notae ecclesiae (the full marks of the church).  Perhaps the latter two areas are where we can find the most ecumenical consensus. 

In my papers on the missional ecclesiologies of Anglican and current Archbishop of Canterbury Rowan Williams and the the Mennonite ethicist (1927-1997) John Howard Yoder, I reflect on the central practices in their ecclesiologies.  For Williams, these are esse notae ecclesiae (essential marks).  Yoder's five practices in Body Politics are bene notae ecclesiae (good marks of the church).

The four practices I draw from Williams are these:

(1) moral discernment oriented by martyrdom (drawn mostly from his book Why Study the Past?)

(2) participation in the sacraments

(3) standing under the authority of Scripture

(4) communicating the Good News drawn from a letter. 

For the latter three practices see, Williams's “Archbishop of Canterbury's Advent Letter,” The Anglican Communion Official Website (14 December 2007). 

Williams hoped that the Anglican Communion would rally around these constitutive practices–esse notae. 

On the other hand, John Howard Yoder describes well the thriving church–bene notae.
(1) Binding and Loosing / reconciling dialogue
(2) Disciples Break Bread Together / Eucharist
(3) Baptism and the New Humanity / Baptism
(4) The Fullness of Christ / Multiplicity of gifts
(5) The Rule of Paul / Open meeting

Yoder does not intend to be comprehensive in his list–he calls these "sample" practices–and therefore, even though they are inspiring, they do not constitute a full ecclesiological foundation (as I argue in my paper).

If you are interested in this topic, you will want to read Miroslav Volf's book After Our Likeness: The Church As the Image of the Trinity. Volf engages Cardinal Ratzinger (now Pope Benedict XVI) and John Zizioulas–both of whom are near the top of the list–over the issue of esse notae.  Volf argues that a community of people is "a church" if they "gather in the name of Jesus" and he adds a few more esse notae.  Thus, he is pretty close to the bottom of the list.  He is arguing that being "at the bottom of the list"–having a free church theology–can be theologically legitimate.

Therefore, as we think about ecclesiological differences with others, I think it is worth reflecting on not only our differences as evident on the spectrum below, but also about the possibility of common purposes in the bene and plene notae.

Disclaimer: I have not read books by all of these people and do not know all of their ecclesiologies that well.  I was just trying to sketch out what I was thinking.  I thought my readers could help me fix the list.

I have put a little bit more about notae (marks) below the list.

60 Theologians on an Ecclesiological Spectrum (from high church to low church)

High church: significant formal requirement for what constitutes "a church"

1. Council of Trent
2. Thomas Aquinas
3. Pope Benedict XVI – Roman Catholic
4. Henri de Lubac – RC
5. William T. Cavanaugh – author of Torture and Eucharist
6. Vincent J. Miller – Roman Catholic and author of Consuming Religion
7. Pope John Paul II – RC
8. Hans Urs von Balthasar
9. Hans Küng – RC
10. John Zizoulas – Eastern Orthodox
11. Augustine
12. Martin Luther
13. John Calvin
14. John Milbank – Anglo-Catholic
15. John Wesley
16. Oliver O'Donovan – Anglican
17. N.T Wright – Anglican
18. Dietrich Bonhoeffer – Lutheran
19. Stanley Hauerwas – United Methodist
20. Rowan Williams – Anglican
21. Craig Van Gelder – Lutheran
22. Patrick Keifert – Lutheran
23. Søren Kierkegaard – Reformed
24. Eugene Peterson – PCUSA
25. Lesslie Newbigin – Reformed
26. Karl Barth – Reformed
27. Mark Driscoll – conservative Reformed
28. Jürgen Moltmann – Reformed
29. T.F. Torrance – Reformed
30. Walter Brueggemann – Reformed
31. Tim Keller – PCA
32. Darrell Guder – Reformed
33. John Piper – Reformed Baptist
34. Reinhold Niebuhr – Congregational
35. H. Richard Niebuhr – Congregational
36. David Bosch – Reformed
37. Wolfhart Pannenberg
38. Richard Hays – UM
39. Len Sweet – United Methodist
40. James Dunn – UM
41. Miroslav Volf – Episcopal and Pentecostal, author of After Our Likeness
42. Scot McKnight – Evangelical Covenant
43. Andrew Jones – Tall Skinny Kiwi
44. Stan Grenz – Baptist
45. Rick Warren – SBC
46. Ed Stetzer – SBC
47. Dan Kimball
48. Menno Simons
49. John Howard Yoder – Mennonite
50. FF Bruce – Plymouth Brethren
51. Bill Hybels – evangelical
52. Andy Stanley – evangelical
53. Rob Bell – evangelical
54. David Fitch – author of The Great Giveaway
55. Tony Jones
56. Doug Pagitt
57. Ryan Bolger – author of Emerging Churches
58. Eddie Gibbs
59. John Wimber – Vineyard founder
60. Peter Rollins
61. Alan Hirsch and Michael Frost – authors of The Shaping of Things to Come.
62. Frank Viola – author of Reimaging Church
63. Donald McGavran and Peter C. Wagner – founders of the "Church Growth Movement."
64. George Barna – author of Revolution
65. George Fox – Quaker, Society of Friends

Low church: fewer formal marks of what is needed to be called "a church"

The language of notae (marks) which I have used here is used differently by different theologians.  Some believe "a church" has certain beliefs, others believe a church has certain traits, others believe a church has a certain structure, others believe it has certain practices.   

The notae ecclesiae can be traced at least back to the Lutheran Church’s Augsburg Confession (1530) written by Philipp Melanchthon and Martin Luther.

The Church is the congregation of saints, in which the Gospel is rightly taught and the Sacraments are rightly administered. And to the true unity of the Church it is enough to agree concerning the doctrine of the Gospel and the administration of the Sacraments.[1]

A revised version of the Augsburg Confession called the Variata, was later signed by John Calvin in 1540. Calvin’s words in The Institutes of the Christian Religion (1536, 1559) are quite similar to the Lutheran document.

The marks of the church and our application of them to judgment: Hence the form of the Church appears and stands forth conspicuous to our view. Wherever we see the word of God sincerely preached and heard, wherever we see the sacraments administered according to the institution of Christ, there we cannot have any doubt that the Church of God has some existence.[2]

Both name the proper preaching of the word and the proper administration of the sacraments as the crucial characteristics of a church.

John Howard Yoder develops four additional marks suggested by Menno Simons in the 1540’s: (1) holy living, (2) brotherly love, (3) unreserved testimony, and (4) suffering.[3]

[1] The Augsburg Confession, article 7 (The Book of Concord). Cited 9 July 2008. Online: http://www.bookofconcord.org/augsburgconfession.html#article7

[2] John Calvin, The Institutes of the Christian Religion (ed. John T. McNeill; trans. Ford Lewis Battles; 2 vols.; LCC; Philadelphia: Westminster Press, 1960), IV, 1, 9. Cited 9 July 2008. Online: http://www.reformed.org/books/institutes/books/book4/bk4ch01.html#nine.htm

[3] John Howard Yoder, “A People in the World,” The Royal Priesthood, 77-89.