‘Gnostic Philosophy’ is actually … basically an anachronistic term that modern scholars do not like to use.
It originated back when all that was really known was that people originally seen as ‘proper’ early Christians referred to various heretical groups as Gnostic.
More research has revealed that there were actually very many different ‘heretical’ groups, such that it only even makes sense to call them heretics after Orthodoxy was formally decided on.
The early Christian movement was extremely diverse and contentious with many groups including or discluding many different texts and theological elements, and basically all of them were simultaneously arguing with, reacting to, and borrowing concepts from each other.
There isn’t really a singular Gnostic version of Christianity or Philosophy. Its an outdated catch all term for distinct and specific groups such as the Valentinians, the Sethians, the Marcionites, Manichaeans… many more.
Many of them actually do have, written down, the secret knowledge that is said to grant one enlightenment or a ticket to heaven upon death once one knows it.
Many others only describe ways of living, thinking and acting that lead one toward the goal of the ‘secret knowledge’ without actually describing the knowledge itself.
Also, a great deal of syncretism, or merging of other religious or mythical tales and philosophical ideas from outside of Judaism and what we now know as modern Christianity was going on, mixing in concepts from Greece, Egypt, Persia, etc.
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Gnosis means knowledge. Gnostic means one with knowledge or one who knows.
Agnosis mean ignorance. Agnostic means one without knowledge or one who does not know.
They are opposites, not equivalents.
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At least the Gospel of Judas seems very much to be written with the idea that Yahweh / The Judaic God is actually evil.
A good number, though not all, ‘Gnostic’ sects wrote about or just rewrote the story of Genesis to make it much more plain that God was actually the one who lied in that story, and viewed the various other cruel acts of the God of the Torah as irreconcilable with a fundamentally ‘good’ deity.
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Long story short, you couldnt reconstruct some kind of ‘true, original’ Christianity if we somehow had a copy of every text of what every various sect in the 1st and 2nd century CE held dear: There are irreconcilable differences and incongruities between the amount we so have.
But thats not so dissimilar from today’s widely varying religions and theological concepts that all identify as Christian.