In many Gnostic systems, various emanations of "God" are known by such names as One, Monad, Aion teleos (αἰών τέλεος "The Broadest Aeon"), Bythos ("depth or profundity", βυθός), Proarkhe ("before the beginning", προαρχή), Arkhe ("the beginning", ἀρχή), and Aeons. In different systems these emanations are differently named, classified, and described, but emanation theory is common to all forms of Gnosticism. In Basilidian Gnosis they are called sonships (υἱότητες huiotetes; sing.: υἱότης huiotes); according to Marcus, they are numbers and sounds; in Valentinianism they form male/female pairs called syzygies (Greek συζυγίαι, from σύζυγοι syzygoi, lit. "yokings together").
This source of all being is an Aeon, in which an inner being dwells, known as Ennoea ("thought, intent", Greek ἔννοια), Charis ("grace", Greek χάρις), or Sige ("silence", Greek σιγή). The split perfect being conceives the second Aeon, Nous ("mind", Greek Νους), within itself. Along with male Nous comes female Aeon Aletheia ("truth", Greek Αληθεια). These are the primary roots of Aeons. Complex hierarchies of Aeons are thus produced, sometimes to the number of thirty. These Aeons belong to a purely ideal, noumenal, intelligible, or supersensible world; they are immaterial, they are hypostatic ideas. Together with the source from which they emanate, they form Pleroma ("region of light", Greek πλήρωμα). The lowest regions of Pleroma are closest to darkness—that is, the physical world.
The transition from immaterial to material, from noumenal to sensible, is created by a flaw, passion, or sin in an Aeon. According to Basilides, it is a flaw in the last sonship; according to others the sin of the Great Archon, or Aeon-Creator, of the Universe; according to others it is the passion of the female Aeon Sophia, who emanates without her partner Aeon, resulting in the Demiurge (Greek Δημιουργός), a creature that should never have been. This creature does not belong to Pleroma, and the One emanates two savior Aeons, Christ and the Holy Spirit, to save humanity from the Demiurge. Christ then took a human form (Jesus), to teach humanity how to achieve Gnosis. The ultimate end of all Gnosis is μετάνοια metanoia, or repentance—undoing the sin of material existence and returning to Pleroma.