Reddit mentions of Augsburg and Constantinople: The Correspondence between the Tubingen Theologians and Patriarch Jeremiah II of Constantinople on the Augsburg Confession

Well there was a correspondence between the ecumenical patriarch and the lutherans. Basically, they essentially agreed on principles of ecclesiology, but disagreed on a lot of doctrine regarding faith, salvation, and sacraments.

There was actually significant dialogue between the early Lutheran reformers and the Orthodox patriarch in Constantinople. The Lutherans sent a Greek translation of the Augsburg Confession and asked the Orthodox to, essentially, proof read it, as they believed that the Orthodox had maintained the Christian faith as set forth by the Apostles and would match quite nicely with the Lutheran beliefs. This book contains the letters and responses translated into English, and it's a really interesting read. You used to be able to find the letters translated online, but I can't find them for the life of me.

A while back I actually asked if anyone knew of any books on this dialogue, and a redditer suggested this book. I'm just now getting around to reading it, but I'm really enjoying it so far, and would suggest it to anyone interested on the topic.

This is a long reply but I do hope you read all of it:

I am convinced that Roman Catholics are far too optimistic about reconciliation (believing it is just a few discussions away), and Eastern Orthodox Christians are far too pessimistic (believing it could never happen).

I am absolutely convinced that natural compromise is impossible. The Orthodox cannot accept Papal infallibility or supremacy (correctly I think; see my flair). More importantly, the Orthodox cannot accept the Filioque, and in addition to that all of the doctrine/thinking leading up to and surrounding the Filioque. The Filioque (and all surrounding doctrine) really is the thing that has been and will be the greatest impediment to reconciliation. If you are interested in reading just how seriously the Orthodox take it, I recommend two books: The Mystagogy of the Holy Spirit and Augsburg and Constantinople.

The former work is St. Photius yelling at some unfortunate recipient about the Orthodox view of the Filioque (do not expect a charitable attitude, unfortunately). The latter work is a verbatim, chronological compilation of letters between some early Lutherans seeking communion with the East, and the then-contemporary Patriarch of Constantinople. Interestingly, the greatest source of debate between the two is the Lutheran acceptance of and support for the Filioque. I initially thought that it would boil down to the sacraments or saints, but no, it devolved into the same basic argument the Christian East has had with the Christian West for centuries, with some Protestant flavor. The latter work contains an actual back-and-forth debate on the matter, whereas the former work, being a single letter, is wholly one-sided. If you're wondering how the Lutheran arguments for the Filioque are relevant to the Roman Catholic arguments for the same, know that the Lutherans essentially copied and pasted Roman Catholic arguments into their letters, so the Patriarch is not really answering Lutheran arguments at that point, but Roman Catholic arguments with Protestant support.

I do think reading the former work is critical to fully understanding the language used in the latter, though I again warn that any Roman Catholic reader will find the former work condescending at least. Even I, while agreeing with St. Photius' points, wondered why it was necessary to take the tone he does. Regardless, if you read both works (the first is very short, the second is very much not), you will have a full appreciation for just how impossible the situation is, on either side. I really want to throw both books at anyone who asks "what's preventing reconciliation?" Even if one does not find the Orthodox arguments convincing, the question will be answered in full.

So again, I am convinced that no amount of dialogue will heal the Schism. I am also, however, most absolutely convinced that Christ desires the healing of the rift (why would He not?), and that as Christ is not a liar, all things are possible through Him. It really is not the responsibility of the laity to work out reconciliation, and attempts at doing so almost always result in behavior that should be brought to confession. We can, however, pray. Christ is not a liar, and says that if two or more are gathered in His name, what they ask will happen. What would happen if not just two or three came together, but rather all the laity on both sides of this painful situation cried out to God for intervention?

"Recently, a group of Finnish scholars has suggested that Luther shares much in common with the Orthodox Church."

That really isn't the impression one gets from reading about the theological exchange between some Lutheran theologians and the Patriarch Jeremiah II that took place in the late 16th century.

What motivated the Lutheran theologians is, I think, the same thing that motivates protestants today to claim some affinity with the churches of the east. But the fact is that Orthodox theology is, for all intents and purposes, Catholic theology. There are a couple of major points of disagreement on doctrine (the "filoque" and the precise role of the papacy) but most differences and disagreements are on matters of discipline (priestly (I do not say "clerical") celibacy, the dating of Easter, etc.)

This book is well worth reading and though it seems one should be able to, I can't find these correspondences for free online anywhere.

http://www.amazon.com/Augsburg-Constantinople-Correspondence-Theologians-Confession/dp/0916586820

Also, maybe it's an honest oversight on the part of OP, but Luther categorically denied the freedom of the human will to choose the good EVEN AFTER conversion and baptism. Something later theologians stepped away from.

http://www.amazon.com/Discourse-Free-Will-Continuum-Impacts/dp/0826477941/ref=pd_sim_b_8

http://www.amazon.com/Bondage-Will-Martin-Luther/dp/1434440656/ref=sr_1_1?s=books&ie=UTF8&qid=1368813064&sr=1-1&keywords=on+the+bondage+of+the+will

EDIT: I'm a convert from Lutheranism and had to wade through all these issues for myself not too long ago.

Here it is in book form. Not sure if it is online somewhere as well.

Since you mentioned both Calvinism and Orthodox, I have two recommendations if you want to read two books where each of these debated and discussed their differences. That said, I do recommend the more 'basic' suggestions first as this isn't light reading. Not in the sense that these two will be hard to read. Rather they are theologically DENSE.

Lutheranism vs. Calvinism: The Classic Debate at the Colloquy of Montbeliard 1586

Augsburg and Constantinople: The Correspondence between the Tubingen Theologians and Patriarch Jeremiah II of Constantinople on the Augsburg Confession

well... At least the Lutherans like the Orthodox and the reformation had nothing to do with us....