I jumped into this thread to make some comments about the Gnostic "Gospels" and their relationship to the New Testament writings (seemingly unnecessarily.)
With regard to the argument of continuity vs. discontinuity of Old and New Testament, Kosta and I have hashed this one out in great detail in the past and I see no need to bore the thread with continued reiterations of our respective views, since neither of us is going to convince the other (nor is agreement necessary). I will make a few comments, and then give Kosta the last word in this particular exchange.
First, I have never said that Judaism as we think of it today (or even as the Christian apologists of the early centuries thought of it) and Christianity are the same faith. One couldn't read the New Testament and come away with that idea. What I have stated is the rather unremarkable assertion that the Church viewed and views itself as in direct continuity with the faith of the Patriarchs and Prophets. Or, as Annalex has put it (quoting Catholic apologists), that Christianity is, at root, Messianic Judaism. One can disagree with this with as many permutations as desired, but I find it hard to see any other self-understanding in evidence in the New Testament or the patristic writings.
Second, in the Beatitudes, Christ is quoting or paraphrasing Old Testament passages in pretty much every case.
St. John Chrysostom gives, as OT sources for Christ's "blessed are the poor in spirit" the LXX texts of Isaiah 66:2, Psalm 50:17, and vs 16 of the Song of the Three Children.
For "blessed are the meek, for they shall inherit the earth", he points out that this is a direct quotation from Psalm 36:11. Etc. The fathers have often done a marvelous job, surprisingly enough, of detailing the continuity between Old and New Testament, showing that the message was there in a form that allowed devout Jews like St. John the Baptist, the Apostles, Nicodemus, and Joseph of Arimathaea to recognize Christ -- and more importantly, of demonstrating that Christ is the very same "He Who Is" of the Old Testament (and as our iconographic tradition makes clear in every single icon of Christ.)
When it comes to loving one's enemies, St. Theophylact in his commentary on this verse from St. Matthew actually uses Moses as a prime example of someone who did exactly that in his life, and says that all saints (intentionally encompassing both Old and New Testament saints) have always done this. The Pentateuch itself (Numbers 12:3) says that Moses was the meekest man in all the earth, doing so in the context of an event where his own brother and sister were speaking against him with enmity. In this event, as in many others, Moses prayed to God for those who had spoken and acted against him.
St. John Chrysostom, writing about the text "think not that I am come to destroy the Law or the Prophets" that follows directly after the Beatitudes asks: "Why, who suspected this? or who accused Him, that He should make a defense against this charge? Since surely from what had gone before no such suspicion was generated. For to command men to be meek, and gentle, and merciful, and pure in heart, and to strive for righteousness, indicated no such design, but rather altogether the contrary."
Regarding David, there are a number of examples of his specifically doing good to his enemies. In fact, one of the direct criticisms that his own "second in command" general levels against him in a particular episode of his life was that David was loving his enemies rather than hating them. The seeds even of this idea and attitude are there in the holy ones of the OT.
Third, as another example of the Messiah being referred to as God in the OT, perhaps the most interesting example is Isaiah 9:6. I wanted to check the details of the LXX before mentioning it, since this is an interesting passage. Most translations of the Hebrew include "Mighty God" as one of the titles for the child who will be born. Brenton's does not have this phrase, so I was curious as to what the various manuscripts indicate. I won't bore anyone with too many of the details, but multiple manuscript traditions, including the Lucianic (i.e. official Byzantine Orthodox) rescension do include the phrase that includes "Mighty God", etc...
Something that I found particularly interesting, given his favorable view of the Hebrew texts is Origen's rescension, where the primary LXX version he was using apparently did not contain this phrase that includes "Mighty God." But, Origen inserted it, marking it with an asterisk -- which was his symbol for a passage that he was drawing from another LXX manuscript, specifically in order to include a Hebrew reading that his primary LXX manuscript had, in his opinion, omitted!
Of course, modern Judaism has their own explanations for the meaning of this passage, as is understandable, so it "proves" nothing. The question, again, is rather whether Christian belief and doctrine was present in nascent but clear forms in the Old Testament, waiting to flower into clarity when Christ actually did appear.
Certainly it was the Resurrection that sent the Apostles back to the Old Testament Scriptures with newly opened eyes -- but when they did, they did not arrive at the conclusion that they had to reject the faith articulated in the Old Testament Scriptures in order to be Christians. They rather came to the conclusion that Christ came to fulfil, not destroy, the Law and the Prophets.
Anyway, this is one that will continue to go on in circles, so I will stop there.
You know, Agrarian, people learn something even, and especially, when they disagree. Just as loving those who love you is no accomplishment, tapping each other on the back because we agree is no effort either. It's a feel-good self satisfaction. So, I really don't understand why you always bid good bye to me other than that I have nothing to teach you even in my ignorance and even in my naivete or just curiosity.
So, I am not responding to you and others that I may have the last word, but to ask more questions. You do a good job of pointing why the Church believes that our faith is "Messianic Judaism," the same faith of the Prophets and OT saints, but you do not tell me why did Christ establish a church and not a synagogue; why did He establish His own royal priesthood? Did he give up on His own? He didn't seek followers among those who knew the faith of Moses, but among fishermen whom He taught true faith. Was there a single rabbi or priest who followed Him? is this not our argument to discredit Martin Luther -- that there was not a single bishop who joined him? Why did the Church develop worship that does not resemble that of the synagogues? Why did we stop Jewish dietary and fasting practices, and so on, if we are one and the same faith as that of the OT saints and Prophets?
If they share the same faith with us, why not then commune with Roman Catholics whose faith is a lot closer to ours than that of Moses and the Prophets? Why do we differentiate between various Christians, yet consider ourselves spiritually in communion with Moses and the prophets?
What you described in your otherwise, as always, excellent presentation is what Kolokotronis (whom I did not ping because he seems disinterested at this point in contributing to this thread)the "sporoi" or "seeds" of our faith, as anticipatory but not fully developed, something we find in many other religions.