 Bultmann, for example, argued that the opening theme of the Gospel of John, the pre-existing Logos, along with John's duality of light versus darkness in his Gospel were originally Gnostic themes that John adopted.Other scholars (e.g., Raymond E. Brown) have argued that the pre-existing Logos theme arises from the more ancient Jewish writings in the eighth chapter of the Book of Proverbs, and was fully developed as a theme in Hellenistic Judaism by Philo Judaeus.The discovery of the Dead Sea Scrolls at Qumran verified the Jewish nature of these concepts.