In my book, I argue that the term ἐπονομάζῃ in Romans 2:17 is in the passive voice and means “publicly recognized as”. Paul’s interlocutor in Romans 2:17-29 is thus a paradigmatic mainstream Jew.
Some scholars have suggested that the interlocutor is a Gentile who “wants to be called a Jew” or who “calls himself a Jew.” This suggestion presupposes that the verb ἐπονομάζειν is being used in the middle voice to refer to a personal act of self-designation in opposition to the public consensus. However, this would not fit with the known usage of the word. This verb is frequently used in the LXX and Josephus to describe the act of giving a publicly available name to an individual or place. Neither the LXX nor Josephus ever use this verb in the middle voice, since such public names are conferred by others or come about through general consensus, never simply through the will of the named individual. The passive voice is, however, used in the LXX and Josephus to mean “publicly known by the name …” This suggests that the verb in Rom 2:17 should also be understood in the passive voice. Hence we should paraphrase, “you are publicly acknowledged as entitled to the name Jew.” Paul is emphasizing the public nature of the interlocutor’s Jewishness, and hence his membership of the mainstream Jewish community situated in the synagogue. The reason that Paul does not simply say, “If you are a Jew…” is not because the interlocutor is really a Gentile with Jewish pretensions, but rather because, as we shall see, Paul is seeking to contest his interlocutor’s understanding of Jewish identity. (p. 148)
The full details of the argument and further references may be found in chapter 5 of the book (p. 148). The chapter is available from the publisher in electronic format:
Windsor, Lionel J. Paul and the Vocation of Israel: How Paul’s Jewish Identity Informs his Apostolic Ministry, with Special Reference to Romans. BZNW 205. Berlin / Boston: Walter de Gruyter, 2014.