Gnosticism is a group of religious ideas from around the 1st century. "Gnosis" is the ancient Greek word for "knowledge", but now more closely means "esoteric knowledge". Gnostic ideas were a main part of early Christianity before being persecuted by other Christians. Gnostic ideas are also found in sects of Judaism and Islam, as well as in alchemy and other kinds of esotericism.
The word "Gnostic" was mostly used by people who were against these ideas. For this reason, some researchers have said that Gnosticism is a false grouping of many separate religious movements. There are many problems for people who research Gnosticism: