What is Gnosticism as noted in the book, Thou Art That?

Gnosticism is a movement named for the Greek term for knowledge, gnosis, describing the intuitive realization that mystery transcends speech. Religions must speak in metaphors. Along with Mithraism, Gnosticism competes with Christianity in the early centuries of the common era. In the mid-20th century, a cache of Gnostic writings, thought to have been destroyed, is recovered at Nag Hammadi in Egypt. The Gnostic gospels shed light on some of Jesus' statements in the canonical New Testament. Jesus claims that the Kingdom of God is spread on the earth unseen and that he and God are in everything.