The Marcosians were a Gnostic sect founded by Marcus, active in Lyon, France and southern Europe from the second to the 4th century. Women held special status in the Marcosian communities; they were regarded as prophetesses and participated in administering the Eucharistic rites. Irenaeus accuses Marcus of seducing his followers, and scornfully writes (Adversus Haereses I. 13, 4) that the whole sect was an affair of "silly women."
The Marcosian system was a variation of that of Valentinus. It retained the 30 Aeons, but called them "Greatnesses" and gave them numerical values. It kept the myth of the fall of Sophia but called it a "Divine Deficiency". Unique to it was the adaptation of the Pythagorean number theory (Isopsephy) to Gnosticism.
System
Marcus holds his knowledge to be the product of a divine revelation of the body of the Anthropos:
Theory of letters
Sometimes Marcus counts the number of letters in a name, sometimes he reckons up the sum total, when to each letter is given its value in the Greek arithmetical notation: sometimes he uses a method which enables him to find still deeper mysteries.
Marcus points out that if we take a single letter, Δ, and write its name at full length, δέλτα, we get five letters; but we may write again the names of these at full length and get a number of letters more, and so on ad infinitum. If the mysteries contained in a single letter be thus infinite, what must be the immensity of those contained in the name of the Propator.
Concerning this name he gives the following account:—When the first Father, who is above thought and without substance, willed the unspeakable to become spoken, and the invisible to become formed, He opened His mouth and emitted a Word like Himself, which being the form of the invisible, declared to Himself what He was. His name consisted of four syllables successively uttered, of four, four, ten, and twelve letters respectively.
It might appear as if we were to understand as the first of these the word ἀρχή; and this name of four syllables and thirty letters seems to correspond to a description of the system of thirty Aeons divided into two Tetrads, a Decad, and a Dodecad. Each letter is one of the Aeons, and contains within itself an infinity of mysteries. Each letter makes its own sound, it knows not the sound of the adjacent letter, nor of the whole, but the restitution of all things will take place when all the letters are brought to make the same sound, and then a harmony will result of which we have an image in that made when we all sound the Amen together.
This comparison shows an interesting point of agreement in liturgical usage between the Gnostics of the 2nd century and the Roman church of the time of Jerome, whose well-known words are "ad similitudinem caelestis tonitrui Amen reboat." What is stated about the limited knowledge of each Aeon may be compared with what Hippolytus of Rome tells of the Docetae (viii. 10).
Tetrad
Marcus pushes into further details his designation of the Aeons as letters of the alphabet. There are twenty-four letters in the alphabet, and twenty-four is the sum of the letters of the names of the first tetrad: The Unspeakable (ἄῤῥητος) Silence (σειγή) Father (πατήρ) Truth (ἀλήθεια)
Followed by those of the second tetrad:
Word (λόγος) Life (ζωή) Man (ἄνθρωπος) Church (ἐκκλησία)
These form the Ogdoad. Again, the Greek alphabet consists of nine mutes, eight semivowels, and seven vowels. The mutes belong to Father and Truth (The Unspeakable, and Silence, of course, do not count); these being mute reveal nothing to man. The semivowels belong to Word and Life, but the vowels to Man and Church, since it was a voice coming through Man which gave power to all.
For the seven heavens, we are told, utter each its own vowel sound, the first A and so on; and it was the sound of their united doxology borne to the earth, which gave generation to all things on the earth. By the descent of Him who was with the Father from the nine into the seven, the groups of Aeons were equalized and perfect harmony produced.
Ἰησοῦς
In the Greek arithmetical notation eight letters are used to denote units, eight tens, and eight hundreds: total 888; but this is exactly the numerical value of the letters in the name Ἰησοῦς. Similarly, the Α and Ω is identified with the περιστερά which descended on Jesus, the numerical value being in both cases 801.