Peter Schäfer reviews a new book, Daniel Boyarin's The Jewish Gospels: The Story of the Jewish Christ, which argues that the Trinity and the incarnation were Jewish ideas:
That the historical Jesus was a Jew, that his followers were Jews, and that the Gospels as well as the letters written by the apostle Paul are Jewish writings, firmly embedded in first century C.E. Judaism—all this has become almost commonplace. After long and bitter battles, this fact now has a foothold not only among historians of ancient Judaism but even among the most dedicated Christian theologians and the old influential school of New Testament scholars who tried to relegate the new message of the New Testament to a less Jewish, more Hellenistic background. Indeed, the pendulum has swung far in the opposite direction, with scholars outdoing each other in proving the Jewishness of Jesus and the New Testament, and arguing that there is nothing in Jesus’s message as reflected in the New Testament that oversteps the boundaries of what might be expected from the Judaism of his day.
The most recent voice in this chorus is Daniel Boyarin’s. His new book has a somewhat misleading title, The Jewish Gospels, because nobody doubts that the Gospels are Jewish. But it is his subtitle, The Story of the Jewish Christ, which makes clear what actually is at stake: nothing less than the claim, announced with great fanfare, that the evolving Christology of the New Testament and the early Church—that is, the idea of Jesus being essentially divine and human, the divine-human Messiah and Son of his Father in heaven—is deeply engrained in the Jewish tradition that preceded the New Testament. … But for Boyarin this extraordinary claim is not enough. He lets himself be gladly carried away by the assertion that even what theologians call the Trinity (the notion of three divine figures, Father, Son, and Holy Spirit) was present among the Jews well before Jesus made his appearance.