Historian Daniel Boyarin’s work on Judaism and Christianity’s shared origins can enrich Nostra Aetate’s vision of kinship, 60 years on.
When three dicasteries of the Roman Curia published Un chemin d’espérance on 16 September, marking sixty years since Nostra Aetate, the note did what anniversary documents are built to do: it reaffirmed continuity. God’s covenant with the Jewish people remains, in the document’s words, irrevocable; the Church’s relationship to Judaism is, per Cardinal Kurt Koch, “constitutive” of Christian identity itself. The text situates this claim in familiar and moving language — Christianity’s Jewish “roots,” a “common spiritual patrimony,” the recognition, drawn from Nostra Aetate’s own fourth paragraph, that the Apostles and many of the first disciples were born of the Jewish people.
It is a generous and theologically serious formulation, one the Church has held to with real consistency for six decades. It also rests, historiographically, on a picture of Jewish-Christian origins that scholarship has substantially deepened since roughly the 1990s — not by contradicting the Council’s insight, but by showing it to be, if anything, an understatement. Understanding how might require a brief detour through the work of Daniel Boyarin.
Who is Daniel Boyarin, and why does he matter here?
Boyarin is a Talmudic scholar and historian of religion, Taubman Professor Emeritus of Talmudic Culture at the University of California, Berkeley, and one of the most influential voices in the study of how Judaism and Christianity took shape as distinct traditions. Trained in rabbinics but reading Christian sources with equal seriousness, Boyarin has spent much of his career arguing — controversially, but with wide and lasting influence — that the two traditions emerged far more entangled with one another, and for far longer, than the standard historical narrative usually allows. His 2004 book, Border Lines: The Partition of Judaeo-Christianity, is the key text for this argument, and it offers Church historians and theologians alike a valuable resource for thinking through exactly the question Nostra Aetate raised but did not have the historiographical tools of its moment to fully answer: what does it actually mean, historically, to speak of Christianity’s Jewish roots?
The old metaphor: Two rivers from one source
For much of the 20th century, the standard account of Jewish-Christian origins — visible in the work of scholars like James Parkes and Marcel Simon — took a fairly simple shape. Second Temple Judaism was the common source. At some identifiable point (the destruction of the Temple in 70 AD, the reputed council at Yavneh, or the missionary activity of Paul, depending on the telling), the two traditions diverged, each thereafter developing along internally coherent, separately bounded lines. The metaphor is fluvial: one source, two rivers, flowing apart. This is the picture Nostra Aetate inherited, and it remains legible in the 2026 note’s language of roots and branches.
Boyarin’s partition: A boundary that was drawn, gradually, by both sides
Boyarin’s central claim is that “Judaism” and “Christianity,” as bounded, mutually exclusive identities, did not yet fully exist for a considerable stretch of the period in which they are conventionally assumed to have already separated. What existed instead was a shared discursive field: common scripture, a shared apocalyptic vocabulary, messianic speculation that did not sort neatly along later confessional lines, and a widespread shared theology that was very much alive within non-Christian Jewish thought as well as the emerging Christian movements. Communities inhabited this field without a settled sense that a border already ran through it.
On this account, the boundary was not discovered at a single rupture; it was constructed, gradually and from both directions, by teachers and authorities on each side working, in effect, in parallel: Justin Martyr’s second-century writings helped define orthodox Christian identity partly by ruling certain positions out of bounds, while rabbinic authorities compiling what would become normative Judaism performed an analogous sorting from the other side. Each community’s growing clarity about itself was achieved partly through this mutual definition. Boyarin dates this partition as substantially complete only by the fourth century, with border communities persisting even later — a history subsequent scholars, notably Annette Yoshiko Reed and the contributors to The Ways That Never Parted (2003), have continued to extend and enrich.
A history that deepens the Council’s insight
None of this stands against Un chemin d’espérance, or against Nostra Aetate before it — quite the opposite. If Boyarin’s picture is right, the “common spiritual patrimony” the Council spoke of is not a metaphorical inheritance comfortably settled in the distant past, but a longer, closer, and more genuinely shared history than the language of roots and branches, on its own, can fully convey. Boyarin’s work does not ask the Church to say less about kinship with Judaism; read alongside Nostra Aetate, it gives good historical reason to say more, and with even greater confidence that the relationship it describes was never merely one of ancestry, but of ongoing, formative company.
Sixty years after Nostra Aetate, that may be the document’s real unfinished invitation: not to affirm the Jewish people’s covenant, which the Church already does unambiguously, but to keep letting historical scholarship show just how well-founded that affirmation is.
