The latter half of what we call Romans Chapter 3 may therefore be considered a succinct overview of Paul's definition of Christianity, which is of course consonant with our God Jesus Christ's definition of Christianity as revealed in the Gospels and as played out afterwards. In Acts, we just saw the Jewish-race Christian Apostles start on their way with non-Christian ties to race-based Israel and to its Law, which then by Christ through Paul were left behind for the purity of the Universal (Gentile) Christianity that Jesus Christ had formed since time immemorial and that He had demonstrated on earth. It is quite natural therefore that immediately after our Romans Chapter 3, we have a Romans Chapter 4 in which Paul combats and annihilates any ideas that the Jewish Law and/or Jewish race are any root of Christianity, but rather explains that compliance with the radically different Christian concept of justification by faith is all that Father Abraham and anyone else have at root been truly honored for by God. This is the philosophically-expounded establishment of the law of faith in Jesus Christ that he just promised us in Romans 3:31, or rather the philosophically-expounded reestablishment of what has always been the true Law without a need to void the Mosaic Law which never was. Disregarding Moses, Romans 4 may be coupled with Galatians 3 as direct answers by Paul to any questions as to who the real and binding children of Abraham are, and to any doubts about who exactly will be blessed and who exactly will be cursed per the promises of Genesis 12. Judging by his letter it appears to be of immediate importance for him to address it from this angle, only surpassed by his Romans 3 approach of more simply saying that all Jews and Gentiles are equally sinners who can only be saved through the blood of Jesus Christ.
Since we have seen historically in Acts, most evidently during Paul's struggles at Jerusalem, how the non-Christian misfactoring in of Jewish race is linked closely to the non-Christian misfactoring in of Jewish Law as to one's salvation, it is good to have Paul's decisive philosophical analysis of what the opening of Romans 4 describes as what his "forefather according to the flesh, discovered in this matter" (Rom. 4:1 NIV). Paul states preemptively, almost sarcastically, that if it turns out that Abraham was justified by Mosaic-Law-type works then he would have had some personal merit to boast about (Rom. 4:2). As before, Paul repudiates what he sets up as a Judaizing proposition, this time mainly with Genesis 15:6, that Abraham "believed in the Lord; and he counted it to him for righteousness." Paul therefore concludes in Romans 4 verses 4 and 5 that Abraham received all his honor and reward from God not because of any good works but because God gracefully and freely gave to him as credit for his workless faith in God.
Notice how Paul has gone back closer to "the beginning" to find the truth about the vastly-overestimated importance of Jewish Law, similarly to how Jesus Christ went back to the very beginning of humanity for the same type of proof in Matthew 19. Yet even more critical here in his own restorative passage is what follows, as Paul takes his proof to the crux of the matter — is being a "child of Abraham" in terms of God's acceptance and favor in any way now tied to being descended from Abraham racially, in other words corporeally or in the flesh?
Romans 4:9-18
9 Cometh this blessedness then upon the circumcision only, or upon the uncircumcision also? for we say that faith was reckoned to Abraham for righteousness.
10 How was it then reckoned? when he was in circumcision, or in uncircumcision? Not in circumcision, but in uncircumcision.
11 And he received the sign of circumcision, a seal of the righteousness of the faith which he had yet being uncircumcised: that he might be the father of all them that believe, though they be not circumcised; that righteousness might be imputed unto them also:
12 And the father of circumcision to them who are not of the circumcision only, but who also walk in the steps of that faith of our father Abraham, which he had being yet uncircumcised.
13 For the promise, that he should be the heir of the world, was not to Abraham, or to his seed, through the law, but through the righteousness of faith.
14 For if they which are of the law be heirs, faith is made void, and the promise made of none effect:
15 Because the law worketh wrath: for where no law is, there is no transgression.
16 Therefore it is of faith, that it might be by grace; to the end the promise might be sure to all the seed; not to that only which is of the law, but to that also which is of the faith of Abraham; who is the father of us all,
17 (As it is written, I have made thee a father of many nations,) before him whom he believed, even God, who quickeneth the dead, and calleth those things which be not as though they were.
18 Who against hope believed in hope, that he might become the father of many nations, according to that which was spoken, So shall thy seed be.
The beginning referenced in Paul's proof is therefore the other end of the same beginning in the proof of Jesus Christ (Mt. 19:4-8). Christ invoked Adam and Eve in Eden where the "beginning" started, whereas Paul referenced Abraham just before his circumcision with which being done the "beginning" ended. This range of time is thus the pre-Jewish era of humanity where all men were in that sense Gentiles, and it coincides with the earliest of the three parts of Luke's genealogy of Jesus (Lk. 3:latter34-38). The Abraham-back-to-Adam-and-God part can indeed be called the "root" of the triad — the other parts being Jesus-to-David and David-to-Abraham — with the family tree of course structured that way to demonstrate the universal originality of Jesus and Christianity. From first-human Adam until Abraham's sign, lack of physical circumcision for the eventual intent and purpose was indeed universal, and there was not a single person yet officially chosen for what was to be the Jews' part of the many Christ-preparatory tasks.
As Jesus and Paul tell us, the first Gentile era of humanity is the historical baseline to understanding the lack of importance of Jewishness even at its very best. Case in point, David's Psalms 32 acknowledgement of grace is also briefly cited in Romans 4 verses 6 to 8, but Paul most beautifully in verses 9 to 18, and also in what follows after, focuses on Gentile-era Abraham to explain why their election from the start had not been physically anchored. Since Abraham himself was as uncircumcised then as the Gentiles are uncircumcised now, the Gentiles can receive just as much favor from God if they have Abraham's faith, whereas the unbelieving Jews will receive just as much condemnation as will any other unbeliever regardless of circumcision — and some words of Christ suggest that if anything the Jews will be the more condemned (Mt. 10:14-15, Mt. 11:10-24, Mt. 12:41-42, Mt. 21:43-45, Mt. 23:30-36, Mk 6:11, Lk. 10:10-15, Lk. 11:31-32). Very directly, Paul in Romans 4 answers concerning Abraham and the Gentiles that, "he received the sign of circumcision, a seal of the righteousness of the faith which he had yet being uncircumcised: that he might be the father of all them that believe, though they be not circumcised; that righteousness might be imputed unto them also" (4:11). Then secondarily, as a preview to Romans 11, he adds as somewhat of an afterthought how this pertains to Jews, "And the father of circumcision to them who are not of the circumcision only, but who also walk in the steps of that faith of our father Abraham, which he had being yet uncircumcised" (4:12). Paul is telling the Jews that if they have the corresponding spiritual faith of Abraham, like he had before he loosely-speaking "was a Jew" physically, then they can be God-favored Christians like the uncircumcised believing Gentiles are God-favored Christians. In other words, the conditions for being a child of Abraham in the spiritual and meaningful sense are for the physically-circumcised Jews the same as they are for everyone else — and these conditions universally exclude race and adherence to the Law as qualifications, of which there are none other than faith which is not really a qualification at all but a free-will mental state.
Justification by faith, a faith that was present in one man Father Abraham, is therefore the root of why God chose to use the Jews for the intended proclamation of that concept to all humanity. As to the honor of being specially chosen for this purpose, by means of their racial election and a Law given to them, it may indeed be said that God favored them in that way. But very amazingly and counterintuitively, which it is a purpose of this essay to contemplate, that Law and that race became a hindrance to their having that faith when it mattered most, and that was when Abraham's Seed Jesus Christ came to give the blessing to all as had been promised (Gen. 12:3). The Jews had gone through so much overprioritized trouble to keep the Law and had built up such a pride in their racial exclusivity that they could not accept the "royal road" (faith alone!) that was revealed to all, for the first time, to have been Abraham's true cause of divine approval. It was therefore the Gentiles who, without this complex history with God, were much more easily upon His incarnation able to accept what God has promised and planned all along, which was only for men and women to accept salvation by the grace of God. The Christian Gentiles therefore eternally received the divine approval that the Jews had a measure of in the past and it happened that the Jews themselves missed out nearly entirely, on the blessing that they had been chosen to help roll out to everyone else! Jesus was the Seed of the promise (Gal. 3:16), and the Jews were to be a labor force for the Seed. They had already mostly-unknowingly been used by God for that purpose — secondhand due to Abraham but still intricately for the end of Christianity. After the universal nature of incarnated Jesus quickly became evident to them, their use became entirely against their wills as they wanted anything but to allow others to be blessed, and they were therefore rejected as Abraham's spiritual children and were broken off of the converted faith tree that he had fathered them onto in its old form. As John had cried in the wilderness that He would, Christ purged them from the floor and instead cast them into the fire. It was quite a turn of events for a nation that God had once guided as if they would have been his rulers of the world, but ridding one's self of one's legitimate God-given kings will tend to do that — a political act like no other that sets up an unspeakably tragic fall. Besides being sinners, the Jews were also no different than us in that they were humanly weak in their moral discipline and that they needed that exceptional human monarch, like some of their past Davidic adopted sons of God were, to have any practical chance of maintaining allegiance to God well enough nationally. About 586 years before Jesus' birth, at the same time when the Davidic Monarchy ceased to rule, it became evident that a loose succession of Gentile kings starting with Nebuchadnezzar of Babylon would instead be God's servants (Jer. 25:9, 27:6, 43:10) and positively fulfill God's preparations for His Son. Then when the time came and the Gentiles much more easily accepted Jesus Christ through faith, they were heavenly awarded with a more regular enshrinement of that other meaning of "royal road," in that they were given legitimate Christian monarchies to rule their nations, to hold their people's allegiance to the true God, and to bring forth fruits in their seasons.
Romans 4 verses 13 to 18 is the snippet that explains all world history after it — why world politics astoundingly moved to Christian dominance in the years after Paul (roughly Christian Rome to 1918) and why our world's current secular and Jewish-heavy democratic hegemony will one day be entirely defeated. Abraham and his seed (his human successors per this usage) are indeed promised by the Abrahamic covenant to be "heirs of the world," but not his seed through the Law but only his seed through the righteousness of faith. As to any notions that those of the Law, meaning the Jewish people proper, be the heirs of the world instead? Verse 14 says "If they which are of the law be heirs, faith is made void, and the promise is made of none effect." In other words, if Jews who do not accept Jesus Christ receive any power by the will and approbation of God, then God is a liar. If the Abrahamic covenant means that Jews have any inheritance on the basis of Jewish race or Jewish law, then the Christian religion is false because (as just demonstrated in Romans 3) Christianity is defined by faith not race or law. The truth echoes Galatians 2:21 that, "if righteousness come by the law, then Christ is dead in vain." Who then are the heirs and who then are the children? Paul in Romans 4:16-18 tells us again, what he and the Gospels have already told us again and again, that all who are of the faith are the children of Abraham. The NIV translates verse 17 wonderfully that "He is our father in the sight of God" — invoking God's spiritual truth over material appearance — and all convey in verse 16 that Abraham is the father of us all if we have his faith. The Abrahamic covenant entirely belongs to the faith which is Christianity, and Christianity in practice is heavily Gentile. Therefore the Abrahamic covenant was indeed fulfilled when it established Abraham as ruler of the world as the spiritual father to many "world-ruling" Gentile nations, when they held the Kingdom of God in their seasons, and will again be fulfilled permanently and yet more thoroughly when his Seed Christ returns to earth. His Kingdom was not "now" of this world when in the judgment hall He was asked by Pilate "Art thou the King of the Jews?," but when Gentiles began nationally claiming Jesus Christ and fighting for Jesus Christ His Kingdom gloriously was of this world for over a thousand years (Jn. 18:33-36). As Christ instructed us, we until He returns pray that God's will again be done on earth, as it is in heaven (Mt. 6:9-10). For the sake of the salvation of our children and our neighbors, most of whom will follow the leader and conform to their environment, we hope to see Christian nations and Christian world hegemony restored as often as possible before the final day of judgment. Christ will still rule in the end for all eternity regardless, but we hope to see again the national Christianity rates of 90% to 99% that were the norm in the First Christian Political Era, so that many more may rule with Him in heaven and/or earth rather than suffer in hell with the masses who have conformingly rejected in the non-Christian democratic era of Satan.