A combination of two religions, as in Israel when the worship of Yahweh, who had led them through the wilderness, became infiltrated, according to the biblical narratives, with beliefs and practices of the Canaanites, who worshipped the gods El and Baal. Such mixtures were sternly resisted by those prophets who looked back to the wilderness period as an ideal (Hos. 13: 4–5; Amos 2: 10–12). Foreign cults were introduced in the reign of Solomon, but from the time of the Exile such influences were excluded; Jewish identity was safeguarded; syncretism was unacceptable, though Hellenization in the last two centuries BCE threatened the traditions and integrity of Judaism.

Christianity related itself to its surroundings but did no more than borrow terminology from Gnosticism, Mithraism, and Platonic philosophy. The theory that Paul blended primitive Christianity with pagan mystery religions of a dying and rising god has had powerful and attractive advocates but is difficult to sustain.