It appears to me that there is a hidden meaning, which is the most obvious and commonly stated one: that Milton was a gnostic and Paradies Lost is an exegesis of his gnostic thought. The mysteries in the subtext identified by the author here seem best explained by the gnostic idea that God is in fact the evil demiurge that created the world, while Lucifer is the true force of good who brings enlightenment and wisdom to the poor people who are as prisoners in the evil world created by God. To be sure, this is not a view I hold to, but I recognize it exists, and it seems the most logical meaning of Paradise Lost.
Anyone who accepts the free gift of salvation through faith alone in Christ alone receives eternal life at the point of faith or belief. As a child of God (John 1:12), member of the royal family of God and royal priest (I Peter 2:5–7, 9) each believer is eternally secure in Christ. At no time can a believer loose his salvation by irresponsible behavior, or any sin of the mind, speech, and behavior. Eternal security is based upon God’s hold on us, not our hold upon Him (John 10:28–29; Jude 24). Since we are saved by faith it is an act of God’s grace to give eternal life (Ephesians 2:8–9; Titus 3:5). Therefore, it is God’s responsibility to keep us in His love in which He is absolutely capable (Romans 8:38–39). Even if we fall away into sin and deny our salvation, the Lord cannot deny us our salvation although He will deny us rewards (2 Timothy 2:11–13). Believers are assigned titles such as “holy”, “beloved”, and “elect” to indicate their eternal security in Christ (Colossians 3:12; Ephesians 1:7, 2:8–20).
Besides the personified notion of Satan, Islam views Satan as temptations in the mind and desire to do evil. Iblis is accordingly also a cosmic force, leading humans (and jinn) astray from good and making them to shayāṭīn as well.  But there is still a distinction assumed between the satanic temptations and the murmurings of the lower self ( Nafs ). The lower self as such, wants the person to do a specific task or to fulfill a desire, while the inspirations of Satan wants the person to do evil in general and returns with another suggestion, after the person resisted.