One reason readers assume Paul is trying to prove that all human beings are sinful is that they understand him to be arguing that no one can keep the law. That means, they think, his opponents must believe that human nature is potentially sinless.
Taking Paul’s statement that, if you “obey the law” (2:25) to mean living a sinless life, is an interpretation without any justification in the Bible. Abraham was a sinful man and yet he is described as obeying God’s law (26:5), albeit in a pre-Sinai context. Likewise, the Psalmist kept the law (Psalm 119:55, 56). Hezekiah kept the law (2 Kings 18:3-6). Zacharias and Elizabeth “were both righteous before God, walking blamelessly in all the commandments and statutes of the Lord” (Luke 1:6). On the face of it, it is entirely Biblical to state that believers “keep” or “obey” the law, despite the fact that they are also sinners.
What modern Evangelical readers want from Paul is an argument that such keeping of the law isn’t really sufficient. There is still sin involved in human behavior that falls short of God’s perfect moral nature. But again, Paul shows no concern for making such an argument. The issue is not the sins that all people commit individually; rather the issue is cultural apostasy and degradation into the most flagrant of perverse sins and the construction of rationalizations to justify such sins (Romans 1:32).
If the idea that Paul means sinless perfect obedience when he says “if you obey the law,” cannot be justified, neither can the idea that “he who is physically uncircumcised but keeps the law” refers to an entirely hypothetical person who cannot exist because no one can live a sinless life since the fall of Adam. On this latter point, one can easily find many Bible stories of Gentiles regarded as covenant members and Jews cast out as covenant breakers. For example, though it takes place before Sinai, Genesis 38 gives us an example of a Gentile who was more faithful to the Abrahamic Covenant that Abraham’s own circumcised seed: “Then Judah identified them and said, ‘She is more righteous than I, since I did not give her to my son Shelah.’ And he did not know her again.”
We find Jesus himself expounds upon examples that took place after the Law was given: “And he said, ‘Truly, I say to you, no prophet is acceptable in his hometown. But in truth, I tell you, there were many widows in Israel in the days of Elijah, when the heavens were shut up three years and six months, and a great famine came over all the land, and Elijah was sent to none of them but only to Zarephath, in the land of Sidon, to a woman who was a widow. And there were many lepers in Israel in the time of the prophet Elisha, and none of them was cleansed, but only Naaman the Syrian'” (Luke 4:24-27).
One notes that the widow was shown to be exemplary in her faith. Naaman too compares favorably to the king of Israel: “So he went, taking with him ten talents of silver, six thousand shekels of gold, and ten changes of clothing. And he brought the letter to the king of Israel, which read, ‘When this letter reaches you, know that I have sent to you Naaman my servant, that you may cure him of his leprosy.’ And when the king of Israel read the letter, he tore his clothes and said, ‘Am I God, to kill and to make alive, that this man sends word to me to cure a man of his leprosy? Only consider, and see how he is seeking a quarrel with me.’ But when Elisha the man of God heard that the king of Israel had torn his clothes, he sent to the king, saying, ‘Why have you torn your clothes? Let him come now to me, that he may know that there is a prophet in Israel'” (2 Kings 5:5b-8).
Jesus referred to the Ninevites and the Queen of Sheba as specifically condemning Jews (Matthew 12:41-42). We also read in Luke 17 of Jesus comparing favorably a Gentile who was his contemporary to some of his Jewish contemporaries. After Jesus cleansed ten lepers, the nine Jews did not return, but only the Samaritan came back to Jesus and gave thanks.
We find another story with this message in Matthew 8: “When he entered Capernaum, a centurion came forward to him, appealing to him, ‘Lord, my servant is lying paralyzed at home, suffering terribly.’ And he said to him, ‘I will come and heal him.’ But the centurion replied, ‘Lord, I am not worthy to have you come under my roof, but only say the word, and my servant will be healed. For I too am a man under authority, with soldiers under me. And I say to one, Go, and he goes, and to another, Come, and he comes, and to my servant, Do this, and he does it.’ When Jesus heard this, he marveled and said to those who followed him, ‘Truly, I tell you, with no one in Israel have I found such faith. I tell you, many will come from east and west and recline at table with Abraham, Isaac, and Jacob in the kingdom of heaven, while the sons of the kingdom will be thrown into the outer darkness. In that place there will be weeping and gnashing of teeth.’ And to the centurion Jesus said, ‘Go; let it be done for you as you have believed.’ And the servant was healed at that very moment.”
In this case, though the centurion was not under the Mosaic Law as such, his behavior toward the people of the Mosaic Covenant gained him a good testimony from the Jews themselves. In the parallel account in Luke 7 we read, “Now a centurion had a servant who was sick and at the point of death, who was highly valued by him. When the centurion heard about Jesus, he sent to him elders of the Jews, asking him to come and heal his servant. And when they came to Jesus, they pleaded with him earnestly, saying, ‘He is worthy to have you do this for him, for he loves our nation, and he is the one who built us our synagogue.'”
So we have several instances of Jews being condemned in comparison to Gentiles, or at least showing themselves as loyal to the Abrahamic covenant as any Jew.
What these Gentile-believer stories all have in common is that in no case were these Gentiles operating by “general revelation.” On the contrary, in each case they were responding to special revelation. This is evidence that Romans 1.18ff is not about how Gentiles are operating in the environment of “natural revelation” but rather how they are acting in the wake of the post-exilic migration of Jews all over the Mediterranean world. It is also evidence that Romans 2:14 is commonly mistranslated. It should not be “For when Gentiles, who do not have the law, by nature do what the law requires, they are a law to themselves, even though they do not have the law.” But rather: “For when Gentiles, who do not have the law by nature, do what the law requires, they are a law to themselves, even though they do not have the law.”
This sets Paul up to point out the advantage of circumcision in 3:1. The Jews count for the most part as a natural family and thus do have the law by birth or nature.
Neither Naaman, nor the Samaritan whom Jesus cleansed, nor the centurion possessed the law by the natural descent from the Abrahamic covenant. Yet, when Naaman honored God’s prophet, and the Samaritan gave thanks to the one who healed him, or the Centurion sponsored a Jewish house of prayer, each one did “what the law requires.”
Paul is simply pointing out, as he describes the climaxing apostasy of Israel and the nations as a whole, that believing Gentiles are justified and unbelieving Jews are not. This supports an important part of his argument that whether or not one is a Jew or a Gentile does not determine one’s final standing with God at the Last Day.
All of this fits well with what Paul writes in his series of quotations from the Hebrew Scriptures. If Paul wanted to prove that no one was able to live a perfect sinless life, we can easily imagine him doing so: “What then? Are we Jews any better off? No, not at all. For we have already charged that all, both Jews and Greeks, are under sin, as it is written: ‘for there is no on who does not sin; (1 Kings 8:46). If you, O LORD, marked iniquities, O Lord, who could stand? (Psalm 130:3). Enter not into judgment with your servant, for no one living is righteous before you (Psalm 143:2). Who can say, I have made my heart pure; I am clean from my sin? (Proverbs 20:9). Surely there is not a righteous man on earth who does good and never sins (Ecclesiastes 7:20). Now we know that whatever the law says it speaks to those who are under the law, so that every mouth may be stopped, and the whole world may be held accountable to God. For by works of the law no human being will be justified in his sight, since through the law comes knowledge of sin.”
The reader will notice I have extracted Paul’s texts (Romans 3:10b-18) from the Hebrew Scriptures and inserted my own. My chosen texts share two important qualities: 1. They all prove universal human sinfulness; 2. Paul does not use them in his argument.
Paul’s texts do show that apostasy and sin have been located in the covenant nation of Israel. They thus support at least the possibility of his claim that Israel has descended into apostasy in his own day, and that membership in Israel is not the determining factor as to whether or not one is justified. This is a thesis that gets more support in Romans 3:27ff and especially in chapter 4. These texts may also be taken as prophetically referring to a time of widespread apostasy in Israel, which is what Paul believes his generation has and is experiencing.
Before introducing God’s purpose in increasing sin and storing up wrath in human history, as well as his solution to that wrath that will result in human salvation (3:21-26), Paul sums up his case in 3:19-20. First he says that Israel’s condemnation means the world’s condemnation. The Law speaks to Israel in order to bring condemnation on the whole world. Secondly, he says that the purpose of Israel or giving the law to Israel was not to make salvation possible for Jews, but rather to introduce a more intense form of sin in the world (as he will expand later in Romans 5:12ff, especially in 5:20). I take “knowledge of sin” here to mean a direct acquaintance with sin. If Romans 5:20 is of any interpretive value to 3:20, it would seem that Paul here is saying that the purpose of the law was not to justify the circumcised but rather to intensify sin to bring about the situation described in 3:19: “that every mouth may be stopped, and the whole world may be held accountable to God.”
But, as I have written above, while this historical process has stored up wrath, it has not revealed God’s wrath. That happened on the cross when God proved Himself righteous and faithful by putting Christ forward as a propitiation by His blood (Romans 3:21-26).