“Pleroma” (Greek for “Fullness”) is the name the Gnostics gave to Heaven. An “aeon” is what the Gnostics called a divine being who inhabited the Pleroma – the Trinity and the angels, more or less.
Much Gnostic terminology, like the words “Pleroma” and “aeon,” seems extremely esoteric and abstruse to the average modern reader. After all, no one talks about a “Pleroma” anymore, and we use the word “aeon” in a different sense than the Gnostics did. This contributes to a belief that Gnosticism was something that was just really wacky and aberrant, whereas proto-orthodox Christianity – the kind of early Christianity that later became “official,” “normal” Christianity – was always simpler and much more, well, normal.
There’s a grain of truth to that impression, in that Gnosticism was indeed more spiritually and intellectually rigorous and demanding than proto-orthodox Christianity was. But to an ancient Greek-speaking audience, Gnosticism and its terminology would have seemed much more familiar and much less bizarre than they do to most of us today.
The words “Pleroma” and “aeon” are excellent cases in point. The New Testament texts Colossians and Ephesians use the word “Pleroma” several times. “Aeon” had a few different meanings in antiquity. Depending on the context, it could mean a long stretch of time, a spiritual being, or a realm in which spiritual beings live. So the Gnostic usage was well within what was standard practice at the time, even though we today no longer use the word in that sense.
The various accounts of the Gnostic creation myth in the Gnostics’ scriptures typically give lavish, meticulous descriptions of how the Pleroma and the aeons originally came to exist. The particulars differ from text to text, but all the accounts share the same underlying plot.
The aeons arose from God the Father passively – that is, they sprang from him without him having gone out of his way to “create” them. The exact method is different in different texts: some say that God’s infinite abundance of thought overflowed and crystallized as new entities, whereas others say that God stared down into the primeval waters and saw his reflection, which became a new being who went on to engender more new beings.
The aeons tended to emanate from God in male-female pairs called “syzygies” (singular syzygy). One of the members of each pair had a grammatically feminine name and the other had a grammatically masculine name. But the Gnostic texts also refer to them in ways that suggest that they transcend gender, so the genders of the aeons evidently weren’t seen as being rigid or absolute.
Different Gnostic texts also give different accounts of the number, names, ordering, and roles of the aeons, much as you’d find in any attempt to give a systematic overview of the angels and other beings who populate Heaven in any version of Christian mythology. But here, too, there’s a common foundation on which most if not all of the Gnostic texts build: a triad of God the Father, the Mother (called “Barbelo” in classic Gnostic texts and likely identified with the Holy Spirit), and Christ the Son. This was the divine archetype of the family, which earthly, human families could reflect in only a flawed and corrupt way. The rest of the aeons tended to be somewhat lesser beings who were in the service of this core heavenly family. Here, again, we can see that the Gnostic model of Heaven, for all its apparent obscurity, wasn’t all that different from the better-known Christian model of the Trinity and a “heavenly host” of angels who attend the Trinity and carry out its wishes.
The Gnostics thought of the aeons as being only semi-distinct entities who remained in some sense identical with God, extensions of particular parts of his being who could nevertheless think and act independently. Like the three members of the Trinity, they were like different fingers on the same hand or different peaks on the same mountain.
No one in the ancient world was a true “monotheist” in the way that we today would use the word; monotheism and polytheism were a spectrum rather than a binary, and a “monotheist” was just someone who believed that one god stood out amongst, and ruled over, an array of other divine beings. So while the Gnostic conception of the Pleroma and the aeons might strike some people as a flirtation with polytheism, by the standards of its time, it was thoroughly – even quintessentially – monotheistic.
If the aeons were somewhat independent while nevertheless being part of God the Father, were they perfect like him or were they flawed by being somewhat other than him? This is a great tension in Gnostic descriptions of the Pleroma, and the Gnostic texts never truly resolve it. One of the aeons, Sophia, the last to come into being, falls from the Pleroma by giving birth to a highly flawed being (the demiurge) on her own, without the involvement of her male partner or the consent of the Father. That seems to imply that the aeons were thought to become less perfect and more flawed as one generation of aeons engendered another and the distance from the original Father increased. Yet only Sophia is described as fallen in any way; the other aeons are all portrayed as if they’re pristine entities. One can argue both sides, but this seems to be a loose end that the Gnostics never quite tied up.
In any case, the Pleroma is depicted as being much like the world of the Forms in Plato’s thought: an ideal, unchanging, eternal realm of which the material world is a corrupted, inferior copy, even though the Gnostics believed that the material world was much further removed from the ideal than it was in Plato.
The Spiritual Significance of the Pleroma
For the Gnostics, Heaven wasn’t just something that existed high in the sky, a subject of theological speculation and of hope for a happy afterlife. The Pleroma’s “Fullness” was also an internal, spiritual state of being that was accessible in this life, through direct experience. The Gnostic Gospel of Philip says, “What is innermost [in a person] is the Fullness (Pleroma), and there is nothing further within. And this is what they call uppermost.”
Salvation meant being saved from a state of horrible deficiency and emptiness and being restored to this otherwise inaccessible divine fullness within oneself. The Treatise on Resurrection holds that when someone’s spirit is saved, “fullness fills what it lacks.” The Gospel of Truth elaborates:
Thus fullness, which has no deficiency but fills up deficiency, is provided to fill a person’s need, so that the person may receive grace. While deficient, the person had no grace, and because of this a diminishing took place where there was no grace. When the diminished part was restored, the person in need was revealed as fullness.
Likewise, in the Secret Book of James, Christ urges his listeners to “Be filled and leave no space within you empty.” And the Gnostic author of the Prayer of the Apostle Paul, as if responding to this commandment, says to Christ, “You are my fullness.”
Thus, the Gnostics’ cosmology was what it was in order to facilitate the inner spiritual transformation they called “gnosis,” the root of the word “Gnostic.”
 Meyer, Marvin, and Elaine Pagels. 2008. “Introduction.” In The Nag Hammadi Scriptures. Edited by Marvin Meyer. HarperOne. p. 11.
 Lewis, Nicola Denzey. 2013. Introduction to “Gnosticism:” Ancient Voices, Christian Worlds. Oxford University Press. p. 53.
 Jonas, Hans. 2001. The Gnostic Religion: The Message of the Alien God and the Beginnings of Christianity. Beacon Press. p. 53-54.
 Brakke, David. 2010. The Gnostics: Myth, Ritual, and Diversity in Early Christianity. Harvard University Press. p. 53-54.
 Lewis, Nicola Denzey. 2013. Introduction to “Gnosticism:” Ancient Voices, Christian Worlds. Oxford University Press. p. 154-156.
 Ibid. p. 65.
 Brakke, David. 2010. The Gnostics: Myth, Ritual, and Diversity in Early Christianity. Harvard University Press. p. 57.
 Ibid. p. 55.
 King, Karen L. 2006. The Secret Revelation of John. Harvard University Press. p. 7.
 Thomassen, Einar. 2008. The Spiritual Seed: The Church of the “Valentinians.” Brill. p. 194.
 Brakke, David. 2010. The Gnostics: Myth, Ritual, and Diversity in Early Christianity. Harvard University Press. p. 61.
 So, for example, Hans Jonas argues that the aeons became more flawed as their distance from the father increased, while Dylan Burns asserts that they were all perfect up until Sophia. See:
Jonas, Hans. 2001. The Gnostic Religion: The Message of the Alien God and the Beginnings of Christianity. Beacon Press. p. 54.
Burns, Dylan M. 2014. Apocalypse of the Alien God: Platonism and the Exile of Sethian Gnosticism. University of Pennsylvania Press. p. 71.
 Brakke, David. 2010. The Gnostics: Myth, Ritual, and Diversity in Early Christianity. Harvard University Press. p. 54.
 Scopello, Madeleine, and Marvin Meyer. 2008. “The Gospel of Philip.” In The Nag Hammadi Scriptures. Edited by Marvin Meyer. HarperOne. p. 174.
 Thomassen, Einar, and Marvin Meyer. 2008. “The Treatise on Resurrection.” In The Nag Hammadi Scriptures. Edited by Marvin Meyer. HarperOne. p. 55.
 Thomassen, Einar, and Marvin Meyer. 2008. “The Gospel of Truth.” In The Nag Hammadi Scriptures. Edited by Marvin Meyer. HarperOne.
 Scopello, Madeleine, and Marvin Meyer. 2008. “The Secret Book of James.” In The Nag Hammadi Scriptures. Edited by Marvin Meyer. HarperOne. p. 25.
 Scopello, Madeleine, and Marvin Meyer. 2008. “The Prayer of the Apostle Paul.” In The Nag Hammadi Scriptures. Edited by Marvin Meyer. HarperOne. p. 17.