Good thoughts. The Church Universal was built initially on Jews … with Gentiles added/blended into.
One could legitimately argue that ALL Christians, with shared genetics dating to Adam/Eva, compose the NEW ISRAEL. God’s chosen ‘reborn’ IN CHRIST.
Interesting discussion.
This is how the Church views it as well. See Lumen Gentium, no. 9; Nostra Aetate, no. 4; Ad Gentes, no. 5; Redemptoris Mater, no. 25; Mulieris Dignitatem, no. 20.
The Church is spiritual Israel (through which all salvation flows) but there is still also “Israel according to the flesh”. I think this is where part of the confusion enters for some. While Israel according to the flesh that has not believed in Christ has been “cut off” from spiritual Israel (through which salvation flows), it is still “chosen”, still dearly loved by God “for the sake of the Patriarchs” (Rom 11: 28), and has a role to play in salvation history, even now. (Although, that love and chosen-ness does not mean that Jews have their own path to salvation, without Christ or His Church.)
Re: “Israel according to the flesh”, see: Rom. 9:3–5; 1 Cor. 10:18.
Additionally, re: “Israel according to the flesh”, the role yet to be played and their corporate identity as “Israel”:
“But this does not mean that there is nothing more to be said about . . . ‘Israel according to the flesh’” (Cardinal Ratzinger, Many Religions, One Covenant, p. 69).
“Hand in hand with this belief goes the other, that Israel still has a mission to accomplish today” (Joseph Cardinal Ratzinger, God and the World: A Conversation with Peter Seewald (San Francisco, CA: Ignatius Press, 2002), p. 149).
“We also know that while history still runs its course even this standing at the door fulfills a mission, one that is important for the world. In that way [the Jewish] people still has a special place in God’s plans” (Ibid., Ratzinger, p. 150).
“If such a dialogue is to be fruitful, it must begin with a prayer to our God, first of all that he might grant to us Christians a greater esteem and love for that people, the people of Israel, to whom belong ‘the adoption as sons, the glory, the covenants, the giving of the law, the worship, and the promises; theirs are the patriarchs, and from them comes Christ according to the flesh, he who is over all, God, blessed forever. Amen’ (Romans 9:4–5), and this not only in the past, but still today, ‘for the gifts and the call of God are irrevocable’ (Romans 11:29)” (Cardinal Ratzinger, “The Heritage of Abraham,” L’Osservatore Romano, December 29, 2000).
Question: “God has not, then, retracted his word that Israel is the Chosen People?” Cardinal Ratzinger: “No, because he is faithful” (God and the World, p. 150).
“They are still Israel, the way the Jews are still Jews and are still a people, even during the two thousand years when they had no country” (Ibid., Ratzinger, p. 148).
“It is in God’s hands, of course, just in what way, when and how the reuniting of Jews and Gentiles, the reunification of God’s people, will be achieved” (Ibid, Ratzinger, p. 150, emphasis added).
“This means that all nations, without the abolishment of the special mission of Israel, become brothers and receivers of the promises of the Chosen People; they become People of God with Israel through adherence to the will of God and through acceptance of the Davidic kingdom” (Ratzinger, Many Religions, One Covenant, p. 28).
Regarding the meaning of “Israel”, while the issue of the “lost tribes” and Jews/Israel is interesting, I’m not sure how important it is in practical terms for us. Christ spoke of the Jewish people repeatedly as “Israel”, St. Peter referred to the Jews of his day as “the whole house of Israel” or “all the people of Israel” (cf. Acts 2:36 and 4:10) and the rest of the New Testament contains many references to them as “Israel” as well, including St. Paul. For example: Luke 7:9, Matt. 2:6, Matt 8:10, Matt 9:33, Matt 10:6, Matt 15:24, Luke 1:80, Acts 2:22, Act 2:36, Acts 4:10, Acts 5:35, Acts 13:16, 1 Cor 10:18. In Matt. 10:5-6, Christ doesn’t even include the Samaritans as “Israel”: “Do not go into pagan territory or enter a Samaritan town. Go rather to the lost sheep of the house of Israel.”
In regard to St. Paul’s specific use of “all Israel” in Romans 11:25, I haven’t found evidence that the Church has viewed this as referring to both Jews and Gentiles together, in spiritual terms. Throughout Romans 11, St. Paul explicitly deals with “Israel” and “the Gentiles” on the natural level, as separate groups. I believe his reference to “natural” branches from the “cultivated olive tree” make clear that he is speaking about Israel according to the flesh, not spiritual Israel in this context. And the ECFS, medievals, Popes and orthodox Catholic scholars of the Church from St. Thomas Aquinas to Lapide and Legrange interpret it that way as well in regard to “all Israel” being saved. Even Protestant scholars see it that way. Fr. M. J. Lagrange, founder of the prestigious Ecole Biblique in Jerusalem, has pointed out that it was really the Protestants—especially Martin Luther—who began denying the eventual restoration of the Jews as a people to Christ. And according to Lagrange, even Protestant exegetes have now returned almost entirely to what he called l’exégèse normale (“the normal exegesis”). Protestant New Testament scholar J. D. G. Dunn states that “There is now a strong consensus that pas Israel must mean Israel as a whole, as a people whose corporate identity and wholeness would not be lost even if in the event there were some (or indeed many) individual exceptions.” [Romans, 681])