The rabbinic treatment of various categories demonstrates a growing tendency towards binarization of identity, common to the spheres of gender and ethno-communal boundaries. Examining the tumtum, the androgines and the Samaritan shows a similar move from allowing intermediary categories in earlier texts to the later casting of such categories in more binary terms as either male or female, Jew or Gentile. The category of the Noahide provides a similar picture: whereas earlier rabbinic texts posit the intermediate notion of a pious non-Jew, later rabbinic texts tend to eliminate the intermediate category of a pious non-Jew, and construct a sharper binary, in which any non-Jew is inherently assumed to be a dis-obedient outsider. Tracing this rabbinic development allows us to see the relation between the rabbinic Noahide and the prohibitions for the Gentiles in Acts 15. This article suggests that instead of explaining rabbinic binarization of identity as a polemic response to Christianity, it may be read, at least in part, as a rabbinic-Christian co-production of mirroring models.