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Previous posts have discussed the vitally important discovery of the "Nag Hammadi library," a group of ancient codices which were probably buried shortly after the the Festal Letter of Athanasius was published in AD 367, condemning "heretical texts" that were not included in the list of "canonical texts."

One of those long-lost texts, rediscovered in 1946 (and taking a rather circuitous route to the awareness of the academic and scholarly community, who took decades to get around to really studying them in earnest) was the Gospel of Philip

Marvin Meyer, in his 2005 book The Gnostic Discoveries: The Impact of the Nag Hammadi Library argues that the Gospel of Philip is a Valentinian text, displaying characteristics of the system of understanding developed by Valentinus, who was born in Egypt around the year AD100 and lived to the age of about 75.  Meyer tells us:
The Gospel of Philip is a Valentinian anthology of meditations on a variety of gnostic themes.  Philip is referred to by name once in the text, and that may be the reason the text is attributed to him.  The arrangement of meditations in the Gospel of Philip seems to be more or less random, though it is possible that sometimes they may be connected to one another by catchwords or the sequence of similar themes.  We do not know where these meditations originated, but presumably they come from different sources.  Layton guesses, "It is possible that some of the excerpts are from Valentinus himself."  [. . .]  Still, through the juxtaposition of ideas and the repetition of themes, this anthology of meditations is able to communicate a Valentinian message of mystical oneness and sacramental joy.  128.
In one of the sayings, the text declares:
God is a dyer. As the good dyes, which are called "true", dissolve with the things dyed in them, so it is with those whom God has dyed. Since his dyes are immortal, they become immortal by means of his colors. Now God dips what he dips in water. 
[. . .]
The Lord went into the dye works of Levi. He took seventy-two different colors and threw them into the vat. He took them out all white. And he said, "Even so has the Son of Man come as a dyer."
translation by Wesley W. Isenberg, available here.
The prominent mention of the number seventy-two here appears to be very significant.  As discussed in previous posts, and in greater detail in the Mathisen Corollary book, the number seventy-two is a close approximation of the precessional constant, the number of years that it takes the background of stars to slip by one degree (see for example the illustrations and discussion in this previous post).  The actual rate is one degree of precession every 71.6 years, but for ease of transmission through ancient myth and sacred tradition, that number was usually rounded to 72 years (it is not too easy to tell a story about 71.6 evil murderers, or 71.6 different colors).

What is remarkable about this appearance of 72 is the fact that detecting and then calculating the precessional constant is extremely difficult -- so difficult that even Ptolemy in his Almagest could only guess at the exact rate of precession and state that it was some number less than 100.  He was not able to pin it down to the actual rate of 71.6 years, or even to the nearest whole number of 72 years.  But many other ancient scriptures and traditions, some long before Ptolemy, use the number 72 in myths that clearly contain strong precessional themes (such as the Osiris tradition), as do many ancient monuments of extreme antiquity (the Great Pyramid is full of precessional numbers).  Clearly, the Gospel of Philip in the Nag Hammadi collection falls into this category of ancient writings.

What is also striking about this passage from the Gospel of Philip is the clear connection between this precessional number and a profound teaching about the human condition.  We are told that "God is a dyer" and that the process of dying makes "those whom God has dyed" immortal.  The image of a "dye works" has something to do with the immortality of the human soul.

We are then told that "The Lord went into the dye works of Levi.  He took seventy-two different colors and threw them into the vat. He took them out all white."  What this teaching is trying to tell us can certainly be vigorously debated.  It is possible that the "dye works of Levi" (who is described in other sacred traditions as a "tax collector") refer to our solar system, where human psyches come to labor under a kind of "taxing" system, but one that apparently causes them to come out a dazzling pure white.  But other interpretations are of course possible.  It may well also have something to do with the concept of "differentiation" and a return to "undifferentiated one-ness" or "unity."

What is so significant about this text, I think, is the fact that the process of purification is linked to a celestial number associated with a celestial or astronomical function (precession).  This clearly illustrates that to the keepers of the ancient wisdom traditions, the knowledge of the subtle astronomical mechanism of precession was far more than simply an amazing piece of scientific understanding (although it was certainly that as well).  The motions of the heavens were perceived as having an intimate connection to a process that was essential to the human soul, purification, and immortality 
This passage all by itself establishes beyond a doubt that the authors of the Nag Hammadi texts possessed subtle and sophisticated scientific astronomical knowledge.  It also appears to establish the fact that they possessed a subtle and sophisticated spiritual understanding as well.