"Gnosticism" is a modern name for a variety of ancient religious ideas and systems prevalent in the first and second century AD. The teachings of the various gnostic groups were very diverse. In his "Dictionary of Gnosticism", Andrew Phillip Smith has written that some branches of Gnosticism taught a panentheistic view of reality, and held to the belief that God exists in the visible world only as sparks of spiritual "light". The goal of human existence is to know the sparks within oneself in order to return to God, who is in the Fullness (or Pleroma).