Source: Birger A. Pearson, "Jewish Sources in Gnostic Literature," Jewish Writings of the Second Temple Period, ed. Michael E. Stone (Philadelphia: Fortress, 1984) 460-461.
"A closer look reveals that the passage posits three classes of men: the perfect, on whom the Spirit of life has descended; 'those who have not known to whom they belong' (NHC II, 26, 33-34), and 'those who did know but have turned away' (II, 27, 22-23). The 'perfect' (=the Gnostics) are, of course, saved. Those in the second group are given another chance in another incarnation, and can thus be saved once they acquire gnosis. Those in the third group are 'punished with eternal punishment' (II, 27, 30). Moreover the entire passage has been placed by a redactor into the discussion of Seth and his race...as an anthropological excursis. Thus it is the race of Seth which is seen to constitute the 'unmovable race' (NHC II, 25, 23) of perfected and perfectible Gnostics."
Pearson is discussing the Gnostic Apocryphon of John, which was probably written in the second century C.E. (according to my Nag Hammadi Library).
The passage seems to believe that certain people are racially predisposed to enlightenment: the race of Seth. Does the Bible agree with this idea? I'm not sure. In John 8:42-44, Jesus says to the Jewish leaders who rejected him: "If God were your Father, you would love me, for I came from God and now I am here. I did not come on my own, but he sent me. Why do you not understand what I say? It is because you cannot accept my word. You are from your father the devil, and you choose to do your father's desires. He was a murderer from the beginning and does not stand in the truth, because there is no truth in him. When he lies, he speaks according to his own nature, for he is a liar and the father of lies" (NRSV).
I'm not sure if Jesus is saying that those who reject him are the literal children of the devil. Arminians like to claim that the Jewish leaders Jesus was addressing chose to be children of the devil, by their own free will. If that is true, why did Jesus tell them that they could not accept his word? Where's the free will, here?
(NOTE: I'm not calling any people-group the "seed of Satan," and I disagree with any denomination that believes in racial hatred. I notice, however, that the concept of Satan's seed appears in various parts of Scripture, and I wonder what it means.)
The Apocryphon of John, however, does not seem to hold that a class of people is unable to receive God. Rather, as far as they're concerned, there are some who do not know to whom they belong, and God will give them another chance in another incarnation. The Christianity that made its way into the New Testament does not really agree with this notion, for Hebrews 9:27 states, "And just as it is appointed for mortals to die once, and after that the judgment[.]" Even if the New Testament does not exclude the possibility that God will have mercy on those who never heard, it's not explicit regarding this gray category, as is the Apocryphon of John. Neither is early Christian literature, as far as I can see.
But both the New Testament and the Apocryphon of John agree that there is an eternal punishment, and that those who fall away from God will suffer it. As Hebrews 6:4-6 states, "For it is impossible to restore again to repentance those who have once been enlightened, and have tasted the heavenly gift, and have shared in the Holy Spirit, and have tasted the goodness of the word of God and the powers of the age to come, and then have fallen away, since on their own they are crucifying again the Son of God and are holding him up to contempt."
Similarly, early Christian literature exhorts Christians to stay in the faith and do good works, since otherwise they will face eternal punishment. There's no "once saved always saved" here, though, of course, the Gnostics apparently assume that the Sethites will persevere in the faith.