The doctrine of salvation by knowledge. This definition, based on the etymology of the word (gnosis "knowledge", gnostikos, "good at knowing"), is correct as far as it goes, but it gives only one, though perhaps the predominant, characteristic of Gnostic systems of thought. Whereas Judaism and Christianity, and almost all pagan systems, hold that the soul attains its proper end by obedience of mind and will to the Supreme Power, i.e. by faith and works, it is markedly peculiar to Gnosticism that it places the salvation of the soul merely in the possession of a quasi-intuitive knowledge of the mysteries of the universe and of magic formulae indicative of that knowledge. Gnostics were "people who knew", and their knowledge at once constituted them a superior class of beings, whose present and future status was essentially different from that of those who, for whatever reason, did not know. A more complete and historical definition of Gnosticism would be:
A collective name for a large number of greatly-varying and pantheistic-idealistic sects, which flourished from some time before the Christian Era down to the fifth century, and which, while borrowing the phraseology and some of the tenets of the chief religions of the day, and especially of Christianity, held matter to be a deterioration of spirit, and the whole universe a depravation of the Deity, and taught the ultimate end of all being to be the overcoming of the grossness of matter and the return to the Parent-Spirit, which return they held to be inaugurated and facilitated by the appearance of some God-sent Savior.
However unsatisfactory this definition may be, the obscurity, multiplicity, and wild confusion of Gnostic systems will hardly allow of wild confusion of Gnostic systems will hardly allow of another. Many scholars, moreover, would hold that every attempt to give a generic description of Gnostic sects is labor lost.