The term Gnosticism is derived from the Greek term "gnosis" which means "to know," and is the root of many English words (dia-gno-sis, kno-wledge, i-gno-re). Gnosticism refers to an exceptionally wide variety of groups who seek "Gnosis," or direct, spiritual knowledge, as opposed to those groups who rely exclusively on belief.

The term Gnosis or Gnosticism has been used in spiritual teachings for unknown centuries. It was used in early Greek philosophy and expressed the foundation of the Greek Mystery Schools, yet it is still debated today which came first: the Greek "Gnosis" or the Sanskrit "Jnana," a term commonly associated with Jnana Yoga, or the path of the knowledge of the divine, whose age and origin is unknown. Nonetheless, there is evidence that the ancient Greek and Hindu schools of divine knowledge learned from each other. Some say that Alexander the Great sought for Gnosis among the Indian yogis.

It is commonly believed that Gnosticism refers exclusively to a handful of philosophical schools of the late Hellenistic and early Christian eras. Yet scholars have recognized that these groups were born from Jewish mysticism, Hellenistic mystery cults, Iranian religious dualism (see Zoroastrianism), and Babylonian and Egyptian mythology, thus the term "Gnostic" would describe a vast sea of religious knowledge.

Scholars present Gnosticism as a collection of movements that opposed the "mainstream" of Christianity, such as those formed by Valentinus and Basilides. It is widely recognized that a large portion of early Christian doctrine (and therefore its descendents) were developed in reaction to these other ideas.

But the actual knowledge and teachings of these "Gnostic" groups were known only from what their enemies wrote (writers such as St. Irenaeus, St. Hippolytus, Tertullian, and Clement of Alexandria).

In the twentieth-century, certain Manichaean and Coptic Gnostic papyri were discovered, providing the first extant Gnostic Gospels and writings. Important texts include The Gospel of Thomas and the Pistis Sophia. These texts opened a world thought lost, and presented to modern humanity the ideas and teachings that gave rise to the persecution of the "heretics" (Gnostics) and the long and troubled history of what has been established as Christianity.

Alternatively, one modern writer described Gnosis as being present in every genuine school of mysticism: "This is the Religion of Wisdom of the ancient Sacerdotal Colleges, of the Gymnosophists, or solitary JINNS from Central Asia, of the Iohanes, Samoans, Egyptian Ascetics, ancient Pythagorians, medieval Rosacrucians, Templars, primeval Masons and other more or less known esoteric Brotherhoods whose list would occupy dozens of pages. This is the Secret Doctrine of the Knights of the Holy Grail. This is the Living Stone of Jacob Gnosis is the flame from which all the religions of the Universe come forth."

In modern times, Gnosticism is a widely abused term, giving rise to many conflicting ideas as to what precisely is meant by it. There are hundreds of "Gnostic" churches, groups, teachings, writers and schools, each claiming to have the true Gnosis, the true knowledge of the divine. These modern groups range from small study groups analyzing the ancient gospels, to movements that claim millions of members. Truly, Gnosticism is not a collection of dead cults; it is a living tradition that has persisted under many faces, but which has never been extinguished, for it is the heart of the human experience: direct, intimate knowledge of higher truths.