Source: “Border lines : The Partition of Judaeo-Christianity” By Daniel Boyarin, University of Pennsylvania Press. 2004
0. Partitioning Religious Identity.pdf

This introductory topic argues that the perceived borders between Christianity and Judaism were not natural, but rather constructed through discourse, much like political borders. The author proposes that the development of heresiology, the defining of "orthodox" belief against "heretical" ideas, was a primary force in this separation, acting as "customs inspectors" to police religious boundaries. This process of creating distinct religious categories, with Christianity inventing the very notion of "religion," led to Judaism's later ambiguous status as both a religion and something more, a dynamic the book will explore through historical texts and theories of identity and categorization.
For thirty years, a man drove a wheelbarrow full of sand across the Tijuana border every single day. The customs inspector, convinced he was a smuggler, dug through the sand each morning but never found any contraband. On the day of his retirement, the inspector finally asked the man to reveal his secret. "What have you been smuggling?" The man replied, "Wheelbarrows."
This story is a powerful metaphor for the history of Judaism and Christianity. The borders we now see as obvious and natural were once invisible. The people who built them, the ancient "heresiologists" and inspectors of religious customs, were so focused on policing minor details—the "sand"—that they missed the massive concepts being smuggled across that would change everything. They missed the wheelbarrows: the very discourses of heresiology and religion themselves.
This post will reveal five of the most surprising and counter-intuitive "wheelbarrows"—the big ideas from history that created the distinct religions we know today.
The common idea of a "parting of the ways" between Judaism and Christianity suggests a natural, gradual separation, like a river branching into two streams. The historical reality is far more dramatic. The border between them was intentionally constructed and imposed, much like a political border drawn on a map by a colonial power, partitioning a territory that once had no dividing lines. As the source text argues, this was an artificial partitioning "much as India and Pakistan, and Israel and Palestine were artificially partitioned by colonial power."