Summarized

The provided text, "Lost Christianities," explores the diverse forms of early Christianity that existed before the dominance of what became the "proto-orthodox" view.

Initially, the speaker outlines the simplified, mainstream narrative of Christianity: Jesus founded a singular church, passed authority to his apostles, who became bishops, and this church spread until Emperor Constantine's conversion made it the state religion. This narrative, while promoted by early bishops for their self-interest, is revealed to be a retroactive construction.

The speaker then introduces four distinct groups of early Christians present in the second century, pre-Constantine:

• Proto-Orthodox: These ultimately "won," establishing a complex Christology (Jesus as fully human and divine) and a monotheistic theology that evolved into the Trinity.
• Ebionites: Jewish Christians primarily in Palestine who continued to practice Mosaic law, rejected Paul's teachings, emphasized Jesus as a prophet (not divine), and had their own lost gospels. They are thought to represent a remnant of the religion's earliest form and may have influenced early Islam.
• Marcionites: Hellenistic (Greek) dualists who rejected the Jewish inheritance of Christianity, considered Paul the most important thinker, and created a limited canon of Paul's letters and edited Luke. They believed the Old Testament God was an evil entity, distinct from the New Testament's benevolent God.
• Gnostics: Drawing on traditions like Platonism, they formulated elaborate mythologies with secret knowledge (gnosis) for an in-group. They believed the material world was created by a flawed "demiurge" (the Old Testament God) and the true God was spiritual. Jesus, for Gnostics, was a divine being who only appeared human, sent to bring salvation through enlightenment. Their texts, like the Gospel of Thomas, often present esoteric interpretations of Jesus's sayings.

The text then discusses the difficulties in reconstructing early Christianities due to scarce and partisan non-Christian sources. Josephus, a Roman Jewish historian, provides only three brief, often interpolated, mentions of early Christian leaders: John the Baptist, Jesus, and James the Just (Jesus's brother).

A key focus is the conflict between James's "Jacobian" church in Jerusalem and Paul's churches in the Greek East. James's group, "the poor," insisted on strict adherence to Mosaic law and asceticism, while Paul advocated justification by faith, not works, and rejected the necessity of circumcision and dietary laws for Gentile converts. Although Paul initially felt defeated by the "super apostles" from James's church who undermined his work, his letters ultimately became authoritative among early Christians, leading to the decline of the Jacobin influence, especially after the destruction of Jerusalem in 70 AD.

The lecture concludes by reiterating that the proto-orthodox view eventually labeled Jewish Christians as heretics (Ebionites/Nazarenes) and absorbed Paul's emphasis on faith, while also reacting to radical purges like Marcionism by expanding their canon. Gnosticism, with its complex secret knowledge, existed often within established churches, making it harder for bishops to eradicate.