I was a little disappointed by this book. It was actually great in terms of its subject matter and content, but it is very definitely a scholarly work, full of jargon and difficult at times to follow. There are losts of references to theory and theorists, which I've rarely understood the purpose of in texts, since so often such ideas are either not integral to the argument or are basic enough that it seems like no theorist need be named.
The basic point, however, if a strong one. Boyarin makes the claim—one that fits well with contemporary sociological and postmodern theory—that the creation of heresy in its modern sense was largely the result of an attempt by both Christian and Jewish writers to create boundaries around their respective faiths. To explore this point, Boyarin shows how the concept of “heresy” was at one point essentially just another means of thinking about a subject—for example, a sect. It's, in fact, Josephus uses when discussing various sects of the Jewish faith in his time. But roughly a hundred years later, Christians aren't just using the term to show differing sects; they're using it to describe only prohibited sects, nonorthodox sects—that is, heretics, as we think of them today. The Rabbis did something similar, declaring those who did not follow their proscribed ways of thinking as minim, that is, heretics. In this way, the Jewish faith transformed into Judaism, rabbinical Judaism.
Before Christianity, Boyarin notes, the concept of religion was tied into one's ethnicity and culture. There really wasn't much of an idea of one having a religion and then also having a nationality. Christianity created this new category of people. But so too did Judaism. It became a religion—for a while.
Curiously, after the Rabbis had thoroughly established control over what constituted Judaism, the idea of Judaism returned to its former roots as an ethnic thing. Today, at least among Jews, one does not so much talk of Judaism as a religion but of people being Jewish, culturally, ethnically, religiously. Thus, one can be a bad Jew—not following the dictates of the faith/nation—but one can never really renounce one's Jewishness.
Another curiosity: Christianity, in defining what was heresy, established itself through attempts at unity. Arguments in the faith aim for that, for a single correct interpretation. Judasim did the opposite. Once the ground rules were established, separating itself from Christanity, it became about arguing about differences of interpretation, presenting all of those as viable—which is what we find in the Talmud.
The case study is one that Boyarin discusses in other places, in a generally more approachable manner: the idea of God's Logos, or Word, or Memra. Boyarin makes the case, made similarly elsewhere in other people's works (Segal, Shaefer, Heiser, Hurtado), that Two Powers theology, the idea that God has a viceroy or partner or subordinate who is very much like him, was very much part of the Jewish religion until Christian times. That's when it became associated with Christanity and by contrast rejected by Judaism. While adoptionist, modalist, and unitarian ideas were made heretical by Christians in favor of a Logos divinity, Jewish Rabbis came to affirm that biblical passages seeming to point to such a figure were really figurative in meaning and that there was solely one God figure, sometimes expressed in different ways (virtually, one might say, modalism, rejected by the Christians). Hence, each faith defined the other, putting up borders accordingly. Those that fall within those borders, borrowing ideas from both sides of the divide are also made heretics, where once they'd have been accepted by either faith; now, as Jerome and some others would put it, they are neither Jews or Christians.
