"The name “Sethian” is a typological category applied by modern scholars to the authors and users of a distinctive group of as many as sixteen treatises, mostly from the Nag Hammadi library, and does not appear to have been an original self-designation. There is no historical record of any group, Gnostic or otherwise, who actually called themselves “Sethians,” even though this convenient term was used by certain of the fathers of the early Christian church who opposed this form of Gnostic thought. During the period 175–475 ce, several of these fathers produced anti-heretical writings in which they refer to Gnostic groups they call “Sethian”: Pseudo-Tertullian Against All Heresies 2, Filastrius of Brescia Various Heresies 3, Theodoret of Cyrrhus Summary of Heretical Fables 1.14 (citing Irenaeus of Lyon Against Heresies 1.30), and Epiphanius of Salamis Panarion 26; 39–40".18
".. many of these treatises refer to a special segment of humanity called “the great generation,” “strangers,” “another kind,” “the immovable, incorruptible race,” “the seed of Seth,” “the living and immoveable race,” “the children of Seth,” “the holy seed of Seth,” and “those who are worthy.” The terms “generation,” “race,” “seed,” and “strangers” are all plays on the tradition of Seth’s birth as “another seed” (sperma heteron) in Genesis 4:25 (J source) and as bearer of the same image and likeness to God as was his father Adam in Genesis 5:3 (P source):
- Genesis 4:25, RSV
And Adam knew his wife again, and she bore a son and called his name Seth, for she said, “God has appointed for me another seed (Hebrew kyīšā tli elohīm zera’ ’ahēr; Greek exanestēsen gar moi ho theos sperma heteron) instead of Abel, for Cain slew him.”
- Genesis 5:3, RSV
When Adam had lived a hundred and thirty years, he became the father of a son in his own likeness, after his image (Hebrew wayyōled bidm–utō ketsalmō; Greek egennēsen kata t–en idean autou kai kata tēn eikona autou), and named him Seth.
Seth’s status as bearer and transmitter (unlike Cain and Abel) and ultimately restorer of the authentic image of Adam, the original bearer of the divine image, was of great significance to the original composers and users of this literature, whether or not they called themselves Sethians or “the seed of Seth.”
Based on the work of Hans-Martin Schenke, the following texts are representative of Sethian thought: from the Nag Hammadi codices and the Berlin Gnostic Codex, the Secret Book of John (NHC II,1; III,1; IV,1; BG,2), Nature of the Rulers (NHC II,4), Holy Book of the Great Invisible Spirit (III,2; IV,2, aka the Egyptian Gospel), Revelation of Adam (V,5), Three Steles of Seth (VII,5), Zostrianos (VIII,1), Melchizedek (IX,1), Thought of Norea (IX,2), Marsanes (X), Allogenes the Stranger (XI,3), Three Forms of First Thought (aka Trimorphic Protennoia; XIII,1); from the Bruce Codex, the untitled text; from Codex Tchacos, the Gospel of Judas and a poorly attested Book of Allogenes (aka Book of the Stranger); and from patristic authors, the accounts of Irenaeus’s Against Heresies 1.29 (Gnostics later identified by Theodoret as Barbeloites), and Epiphanius’s Panarion 26, 39, and 40 (Gnostics, Sethians, and Archontics, respectively).
In varying ways, these treatises display a number of recurrent mythological features that Schenke considers to form a core doctrine or myth on the basis of which one may characterize a document as “Sethian”: the self-understanding of their readers as the spiritual “seed” (descendants) of Seth, who is also their heavenly-earthly savior, and a supreme trinity consisting of the Father (Invisible Spirit), the Mother (Barbelo), and the Child (Autogenes), who in turn establish Four Luminaries (Harmozel, Oroiael, Daveithai, and Eleleth, often conceived as the dwelling places of the heavenly Adam, Seth, and the seed of Seth), the last of whom is responsible for the appearance of Sophia and, through her, for the material world and its evil fashioner and ruler Yaldabaoth/Sakla (or Saklas)/Samael and his demonic powers, who try to destroy the seed of Seth by flood and fire but are thwarted by the Mother’s saving interventions: as a divine voice revealing the existence of the archetypal human, as the spiritual Eve, and ultimately as the heavenly Seth or Christ, who bestows a saving baptism often called the Five Seals.
* In the hands of Sethian Gnostics, these biblical functions of Sophia were distributed among a hierarchy of feminine principles: (1) an exalted divine Mother named Barbelo, who, as the First Thought (“Protennoia,” “Pronoia”) of the supreme deity (the Invisible Spirit), is the ultimate savior and enlightener; (2) a lower figure named Sophia, who gave rise to the actual creator (“Yaldabaoth,” “Sakla,” “Samael,” the first archon) of the physical world, who in turn incarnated portions of the supreme Mother’s divine essence into human bodies; and (3) the emissary figure of the spiritual Eve (“Epinoia”), who appears on the earthly plane to alert humankind (Adam) to its true affinity with the divine First Thought. Final salvation would be achieved by the supreme Mother’s complete reintegration of her own dissipated essence into its original unity.
The functions of these various feminine wisdom figures were interconnected by means of a myth that narrated the vicissitudes of knowledge (gnosis) itself ...
... The Mother’s further salvific appearances throughout subsequent history in various guises (e.g., as a luminous cloud, as ethereal angels, as Seth himself, or as Jesus) and ritual contexts (mainly baptism) continue to awaken humanity’s potential self-awareness of its essential divinity to full actuality. Salvation is thus the awakening of the fallen divine self-knowledge and a reintegration into its original condition, which is actualized through the individual Gnostic in the act of coming to know oneself by re-enacting the myth of the vicissitudes of knowledge itself.
The Sethian treatises divide themselves into two basic groups depending on the way one attains salvific enlightenment. One group of tractates, Secret Book of John, Revelation of Adam, Holy Book, Three Forms of First Thought, Gospel of Judas, and perhaps Nature of the Rulers, conceptualizes the means of salvation as a horizontal, temporally successive sequence of revelatory descents into this world by a heavenly savior ...
In this first, “descent pattern” group of treatises, the salvational process is instigated by the Mother of the Sethian trinity, usually called Barbelo, who—unrecognized by the hostile cosmic powers—appears at crucial points in primordial history, although her final appearance in contemporary times often occurs in a masculine guise, such as the Logos (Word) or Seth or Jesus, and the instrument of salvation is frequently the baptismal rite called the Five Seals.
In the second, “ascent pattern” group - Zostrianos, Allogenes the Stranger, Three Steles of Seth, and Marsanes, conceptualizes the means of enlightenment and salvation as a vertically oriented ascent whereby a visionary practitioner illustrates a succession of mental states in which one is cognitively assimilated to ever higher levels of being (and those beyond being itself). The possibility of enlightenment as revealed by the visionary experience of various illustrious figures—Zostrianos, Allogenes, and Marsanes—exemplifies a contemplative technique to be implemented by the individual Gnostic either alone or in concert with other similarly instructed adepts.
'The Sethian School of Thought', in 'Epilogue: Schools of Thought in the Nag Hammadi Scriptures', in turn, in Marvin W Meyer, The Nag Hammadi Scriptures: The Revised and Updated Translation of Sacred Gnostic Texts, Harper Collins, 2010