 In the first half of the 20th century, many scholars, primarily including Rudolph Bultmann, have forcefully argued that the Gospel of John has elements in common with Gnosticism.Christian Gnosticism did not fully develop until the mid-2nd century, and so 2nd-century Proto-Orthodox Christians concentrated much effort in examining and refuting it.To say John's gospel contained elements of Gnosticism is to assume that Gnosticism had developed to a level that required the author to respond to it.