Gnosticism (gnosis simply means direct knowledge), as practised by early Christian heretics, contains two basic tenets. The first is dualism, which can, according to Michael Baigent and Richard Leigh, be defined thus:

Dualism, as the word itself suggests, presupposes an opposition, often a conflict, between two antithetical principles, two antithetical hierarchies of value, two antithetical realities. In dualism, certain aspects or orders of reality are extolled over others. Certain aspects of reality are repudiated as unreal, or inferior, or evil. In its distinction between soul and body, between spirit and 'unregenerate nature', Christianity is, in effect, dualist.

The second tenet concerns the evil of matter:

Matter was rejected as intrinsically evil. Material creation, the phenomenal world, was deemed to be the handiwork of a lesser and malevolent god. In consequence, matter and material creation had to be transcended in order to attain union with a greater and truer god, whose domain was pure spirit; and it was this ' union that the term 'gnosis' signified ... [Gnostic] thinking had probably originated in the similar dualism of Persian Zoroastrianism. It was subsequently to surface again in Persia, under a teacher known as Mani, and to be called Manicheism.