The Savage in Judaism exposes and challenges the opposition between Judaism and "savage" religions that has shaped the conceptualization of Judaism in the discourses of modernity. Since the Enlightenment, Judaism has typically been regarded as superior to other religions. This judgment gave rise to the conviction that interpreters of Judaism had little if anything to learn from either the discipline of anthropololgy or comparative inquiry. This book, by contrast, aligns itself with a growing trend that is seeking to collapse the distinction between Judaism and savage religions. It does so, by recounting the history of that opposition and by a series of studies showing how differently Judaism appears when passed under the gaze of anthropological inquiry and cross-cultural analysis. Topics includes circumcision, impurity, and dietary restrictions.

In ancient Jewish culture the ideas of purity and impurity defined the socio-cultural boundaries between Jews and Gentiles. Hayes argues that different views of the possibility of conversion, based on varying ideas about Gentile impurity, were the key factor in the formation of Jewish sects in the second temple period, and in the separation of the early Christian Church from what later became rabbinic Judaism.

The book describes in detail the ritual purity system of the Hebrew Bible, and its development into the system of the rabbis. Certain human conditions require purification before contact is made with holy foods or areas. Recent scholarly theories (Milgrom, Neusner, Douglas) are discussed, and new theories are proposed for the origin of the Red Cow and Scapegoat rites. It is argued that the impurities concerned all derive from the human cycle of generation, birth and death, from which the Sanctuary is to be guarded; not because it needs protection from demonic powers (as in other ancient purity systems), but because of the reverence due to the divine presence. While the priestly code of holiness displays traces of earlier conceptions, its ritual has lost urgent salvific force, and has become a protocol for the Temple and a dedicatory code for a priestly people; the sources distinguish it from universal morality.