C Cranfield and Karl Barth are almost alone in connecting v14 of Romans chapter 2 with v13b. Cranfield writes:
“The most natural explanation of the “For” (at the beginning of v14) would seem to be that these verses are thought of as confirming v13b…. v13b, which might at first sight appear to conflict with “And also for the Greek” of v10, does not in fact do so, since those Gentiles who do the things the law requires stand in a real positive relation to the law (v14b & v15a) and so may be regarded as included in the reference of the “doers of the law” in v13b” .
In other words, Cranfield sees a continuing between v10 and v13. The greek can do good and receive honor and glory and peace (which is salvation), v10, and therefore the doers of the law who will be justified can also be greeks. V13 refers to separate groups of people, those who hear the law (and so have the law physically – the jews) and those who do the law (anybody, Jew or Greek). To connect v14 to v12a would imply that v12b-13 is a form of parenthesis or explanation. I do not see such a division. Paul is merely establishing the fact that to have the law, to hear the law, does not mean you are saved.
The word ‘Gentiles’ is without the definite article, which suggests that it refers to some gentiles, not all gentiles. As we have said, Moo et al see this as referring to gentiles who are not converted while Cranfield / Barth sees these gentiles as Christians.
The next part of the verse: who do not have the law do by nature what the law requires has some difficulties. Traditionally the word nature has been taken with what follows. This means the verse would say the gentiles, as a result of their possession of natural law, do some of the things required by God’s law instinctively.
This is what Moo argues. He says that Paul is almost certainly referring to a greek / stoic tradition that all human beings possess as unwritten law, an innate sense of right and wrong. Hence, we do the law by nature. Moo says that for this reason, this cannot refer to believing gentiles, because believers do the law by grace, and not by nature.