The Jewish question

28 For no one is a Jew who is merely one outwardly, nor is circumcision outward and physical. 29 But a Jew is one inwardly, and circumcision is a matter of the heart, by the Spirit, not by the letter. His praise is not from man but from God (Rom 2:28-29).

This is a prooftext for supersessionism. Here's one example:

My thesis is that the reference in Rom 11:26 to “all Israel” should be interpreted as a Pauline redefinition of the concept “Israel” in light of the great mystery that has been revealed in the person and work of the Lord Jesus Christ. 

Now part of Paul’s refutation of this sadly mistaken assurance involves a redefinition of the value of circumcision. He states, at the end of chapter two: “He is not a Jew who is one outwardly; neither is circumcision that which is outward in the flesh. But he is a Jew who is one inwardly; and circumcision is that which is of the heart, by the Spirit, not by the letter.” In fact, Paul waxes so bold as to ask a most radical question: “If therefore the uncircumcised man keeps the requirements of the Law, will not his uncircumcision be reckoned as circumcision?” (v. 26). 

Do you see what Paul is doing here? He is upsetting traditional Jewish theology by asserting that it is not circumcision or membership in the community of Israel that determines salvation but law-keeping. “Not the hearers of the Law are just before God, but the doers of the Law shall be justified” (v. 12). If so, then it is theoretically possible that many Jews will be condemned and many Gentiles saved. A new criterion is being introduced to define those who are the legitimate heirs of the Abrahamic promises. A new definition of Israel is emerging. 

http://www.upper-register.com/papers/Rom1126.pdf

I'll use that as a foil. There are some basic problems with saying Paul has redefined "Israel". 

i) One problem is the "Jewish question". Is God faithful to the promises he made to the patriarchs (e.g. Rom 3:4; 11:2)? If the recipient of a promise can be "redefined", after the fact, then in what respect has God made good on his promises? If God can swap out the original referent and swap in another referent, then the promise is equivocal and vacuous, since there's no continuity between promise and fulfillment. Transferring the promise from one party to another is a broken promise, is it not? I made you a promise, but I've kept my promise by doing that for someone else! Lee might say gentiles were always included in the promise to Abraham, but in that event, where's the "redefinition"? 

ii) There's nothing innovative about Paul's distinction. Distinguishing literal/physical from figurative/spiritual circumcision (or equivalent metaphors) goes straight back to the Law (Lev 26:41; Deut 10:16; 30:6) and the prophets (Jer 4:4; 9:24-25; 31:33; Ezk 36:26-27; 44:7). 

Perhaps, though, what Lee means by "traditional" is Second Temple theology rather than OT theology. 

iii) Scholars often use the term "ethnic Israel" and "ethnic Jew," but contextually, a more accurate term might be "genealogical Jew," in the sense of a lineal descendent of Abraham. 

iv) Is Paul bifurcating Jewishness into two separate kinds of Jews? Rather than a stark dichotomy, Paul's contrast may concern two overlapping categories, where "inward" Jews are a subset of "outward' Jews". That involves an asymmetrical relation: while all "inward" Jews are "outward" Jews, not all "outward" Jews are "inward" Jews. Both groups are genealogical Jews. Both groups are Jews on the outside. That's the general category. But within that larger class are Jews on the inside. If so, that preserves the continuity of the promise inasmuch as faith an OT criterion no less than a NT criterion. 

v) But it doesn't eliminate all possible ambiguity. What's the status of gentile converts to Judaism? Would Paul classify them as Jews? What about intermarriage? If marriage between a Jew and a gentile issues in offspring who subscribe to Judaism, would Paul classify that generation as Jewish?

vi) A related ambiguity is the fact that the 1C marks a transitional phase. Before the advent of Jesus, a messianic Jew wasn't a Christian in particular, since he didn't know that Jesus of Nazareth was the promised messiah. But after the advent of Christ, to be a messianic Jew, from a Pauline perspective (and NT writers generally) is to be a Jewish believer in Jesus. So what qualifies one to be an "inward" Jew in OT and Intertestamental times is insufficient vis-a-vis what qualifies one to be an "inward" Jew in Christian times. Paul was living and writing in that transitional phase. 

Apropos (v-vi), there remain some ambiguities regarding Jewish identity, as Paul defines it. Can we tie up the loose ends? Are there borderline cases?