Gnosticism (from the Greek word gnosis which means 'knowledge') developed in the second century AD. It was a complex philosophical system which emphasised the importance of obtaining secret knowledge for salvation.
This secret, spiritual knowledge was not available to all but only to the elect. Salvation was being freed from the material world, which was evil, and reunited with the spiritual, which was good. This dualism between the spiritual and material led some Gnostic groups to live austere lives of self-denial (asceticism) since the physical body was part of the material world.
Recognising the character of Gnostic thought indicates how badly they have been misrepresented by The Da Vinci Code. In the novel Gnostics are said to be the original Christians whose Jesus was a very human prophet married to Mary Magdalene. This is inaccurate on at least three counts.
First, as we have seen, Gnostic thought developed nearly a century after Jesus. The Gospels of the New Testament predate the earliest Gnostic Gospels. Therefore, the claim that the Gnostic texts represent original Christianity is false.
Second, in the Gnostic Gospels, salvation comes from hearing and understanding the esoteric teaching of Jesus not from believing in his death and resurrection. Christianity is, and always has been, a historical religion. The Jesus we encounter in the Gnostic Gospels is only human in appearance. How could the incorruptible spirit be united with the corruptible material?
In reality, many Gnostic groups, especially the more ascetic ones, would have despised the idea that Jesus was married. How carnal!
Third, and perhaps most importantly, second and third century Gnostics were not arguing for inclusion in what was understood to be Christianity. They were arguing that they held the exclusive key to salvation over and against traditional Christianity.
Gnosticism was not another denomination within the Christian Church like Baptists and Anglican. Gnosticism was a different religion altogether. Christians disagreed with Gnostics about God, about the goodness of creation, about Jesus' humanity, about how we are saved and about who can receive that salvation.
Christians believed that God had created the material world and declared it good; they believed, as we have seen, that Jesus was fully human and fully divine; they believed that we are saved by faith in Jesus's death and resurrection and that all people, not just the elect, can receive that salvation.
The portrayal of Gnosticism in The Da Vinci Code is inaccurate and selective. Once again, the brevity of this booklet prevents us from discussing this any further. I would highly recommend Darrell Bock's chapter on Gnosticism for further reading (Code 4: Do the So-Called Secret, Gnostic Gospels Help Us Understand Jesus?).
While The Da Vinci Code adamantly affirms that the New Testament Gospels are unreliable sources of information about Jesus which cannot be trusted the reality is far different. Bart Ehrman, after an examination of the Gnostic texts and the New Testament concludes,
And so, whether we like it or not, whether we are Christian believers or not, whether we are historians or televangelists or preachers or Sunday school teachers or just regular lay folk with an interest in knowing about the life of Jesus (and about such things are his alleged marriage to Mary Magdalene), whatever our situation and whatever our personal beliefs, we are more or less restricted to the Gospels of the New Testament in trying to learn what Jesus said and did. (2004, 109-10)