Without a doubt Christians.
Throughout his epistles, Paul confronts objections to his teachings. In this case he is responding to potential objections to Romans 2:6-11.
Rom 2:6 who “will pay back to everyone according to their works:”
Rom 2:7 to those who by perseverance in well-doing seek for glory,
honor, and incorruptibility, eternal life; Rom 2:8 but to those
who are self-seeking, and don’t obey the truth, but obey
unrighteousness, will be wrath and indignation, Rom 2:9 oppression
and anguish, on every soul of man who does evil, to the Jew first, and
also to the Greek. Rom 2:10 But glory, honor, and peace go to every
man who does good, to the Jew first, and also to the Greek.
Rom 2:11 For there is no partiality with God. (WEB)
Paul's argument goes something like this: If God is truly impartial in His judgement (2:11), judging both Jew and gentiles according to the same standard, where does that leave the law? Paul understood the validity of this looming question. Because the gentiles were not recipients of the law (see Eph 2:12). Only the Jews were "under the law" given to Moses. Gentiles had no knowledge of the law, and by implication could not attempt to follow it.
Given those facts, Paul must present a strong argument to defend his conclusion that God is impartial. If not, one might conclude that gentiles should be judged by strict conformity to the Mosaic law, including circumcision like many of the early Jewish Christians. But Paul counters this notion. God is not going to judge Gentiles by a law never given to them. But God favors those who are doers the law not those who are only hearers (those who heard it read in synagogues).
Paul then points to a mysterious group of gentiles who are:
- Called righteous and justified.
Rom 2:13 For it isn’t the hearers of the law who are righteous before
God, but the doers of the law will be justified
- Have a law written on their hearts/regenerated. (Jer 31:33, Heb 10:16).
Rom 2:15 in that they show the work of the law written in their
hearts,
- Have thoughts accusing them (as all seed of Adam) but have thoughts excusing them on the day of judgement.
their conscience testifying with them, and their thoughts among
themselves accusing or else excusing them) Rom 2:15b
One may wonder how pagan gentiles could ever be called doers of the law. Especially given Paul's indictment against them in Romans 1:21-32. They only way they could be doers of the law is by following the law of righteousness found in Christ.
Summary
One reoccurring theme throughout Paul's writings is gentile inclusion into the people of God. As mentioned in the above answers, both believing Jews and gentiles were formed by the Spirit into one new man (Eph 2:15).
In Romans 2 the text does not seem to imply Paul was making a hypothetical statement. Its contexts points towards judgement "according to works", which we find throughout the Hebrew scriptures and NT. No one doubts those spoken of in Romans 2:25-29 are Christians, yet they are described in the same terms as those in 12-16. That leads me to believe Paul's rebuttal to the potential objection goes something like this: Although Gentiles were not given the law, they (by the nature of the Spirit's work) obey the very requirements of the law through faith in Christ. Two supporting passages of this makeshift paraphrase is below. Check them out.
Rom 8:3 For what the law couldn’t do, in that it was weak through
the flesh, God did, sending his own Son in the likeness of sinful
flesh and for sin, he condemned sin in the flesh; Rom 8:4 that the
ordinance of the law might be fulfilled in us, who walk not after
the flesh, but after the Spirit.
Rom 9:30 What shall we say then? That the Gentiles, who didn’t follow
after righteousness, attained to righteousness, even the righteousness
which is of faith; Rom 9:31 but Israel, following after a law of
righteousness, didn’t arrive at the law of righteousness.