One of the remarkable characteristics of the Mishnah is how little information the text reveals about itself, its origins, authors, history, sources, and social setting. The two Talmudim and the rest of rabbinic literature are more forthcoming with such information (whether the information is reliable is another matter entirely), but, at no point, do the rabbis feel constrained to identify their opponents precisely or to describe competing groups in Jewish society. The rabbis often refer to gentiles, heretics, and irreligious or nonobservant Jews, but had no interest in describing the manifold varieties of each of these categories. Rabbinic literature is an “internal” literature, written by, about, and for the rabbis.
Shaye J.D. Cohen, From the Maccabees to the Mishnah (Philadelphia: The Westminster Press, 1987), 225.