"So, if a man who is uncircumcised keeps the precepts of the law...."We don't even need to finish the sentence. Paul's contemporaries surely would have found the premise itself to be contradictory. They likely would have asked "How can one be uncircumcised and keep the law when circumcision itself is a key component of the law?" In order to answer that question, Paul returns to the very origins of circumcision.
In Romans 4, Paul supports and illustrates his claim that righteousness apart from the law is possible by recounting the story of Abraham. Abraham was the father of Israel. God promised Abraham that if he followed God then he would be made the father of many nations and that all the people of the earth would be blessed by his offspring. As such an important figure, Abraham serves as a sort of paradigm for all of Israel. There is a sense in which what is true for Abraham is true for God's people. He is not merely one example among many Paul could have utilized. Abraham, more so than any other individual figure, is really the example when it comes to the identity of Israel. And it was with Abraham that circumcision became an identifying mark of Israel. God commanded Abraham to be circumcised as a sign of the covenant that God had made with Abraham. God commanded that all of Abraham's descendants be circumcised as well as a sign of their participation in this same covenant.
Here we begin to get a sense of why circumcision, which probably seems an arbitrary and inconsequential thing to us, was of such great importance to the Jewish people. It was commanded by God and it was a sign of God's call to Abraham, the very beginnings of Israel. It was a sign of God's promises to Abraham and his descendants. It was a sign of Israel's continued participation in that very same covenant. It was nothing less than a symbol of God's faithfulness to Israel and Israel's faithful response. It is probably not an overstatement to say that circumcision was synonymous with what it mean to be Israel, to be God's people. Abraham is precisely the figure that Paul's opponents would have cited (and did, if Galatians is any indication) as the reason why one must be circumcised in order to keep the law and participate in God's covenant. It is because of Abraham, they would have argued, that one can not keep the law and remain uncircumcised.
It is a demonstration of Paul's keen mind at work re-reading the scriptures in light of Christ that he managed to use the very figure who formed the crux of his opponents argument to make his own point which was precisely the opposite of theirs. The critical turn in Paul's argument is found in 4:9-11:
"Is this blessing then only for the circumcised or also for the uncircumcised? For we say that faith(fulness) was counted to Abraham as righteousness. How then was it counted to him? Was it before or after he had been circumcised? It was not after but before he was circumcised."God counted Abraham as righteous in Genesis 15. God did not require Abraham to be circumcised until Genesis 17. God counted Abraham as righteous before he was circumcised. That is, Abraham actually serves as the perfect example for Paul's argument because Abraham was considered righteous apart from circumcision, apart from the law. The scriptures themselves claim that God considered Abraham righteous because of his faith(fulness).
It is faith(fulness), Paul radically claims, not circumcision or adherence to the law which has always been the true mark of God's people. Abraham demonstrated this same faith(fulness) by trusting God even when he was old and had no heir, even when God demanded the sacrifice of his heir. Abraham was righteous not because of circumcision but because he lived faithfully before God and what is true for Abraham is true for all God's people. When there is not yet a God-given law, when that God-given law fails to produce righteousness, when God is doing crazy things like promising a fatherhood of nations to an old and childless couple or raising God's messiah from the dead, "the righteous out of faithfulness will live."