Yes it is at its core gnostic, brought in by Augustine.
Augustine is the first in Christian history to introduce the concepts and idea that for example no one can respond positively to the gospel appeal unless they've been regenerated first this concept/idea that God has to choose you or elect you started in the fifth century.
Not true about him being the "first" Christian. The Doctrines of Grace are taught throughout the bible by the inspired writers chosen by God to record his Truth.
Now, I have a question or two for you, sir: Is there any record anywhere in the world, or in the bible, of the physically dead (souls that have separated from their bodies) having the ability to respond to natural stimuli? If not, then what would compel you to think that spiritually dead (souls separated from the Spirit of Life) would have any ability to respond to spiritual stimuli?
Secondly, Is there any record anywhere in the world, or in the bible, of the physically resurrected asking to be raised from the dead prior to their death? If not, then what would make you think that spiritual resurrection is a result of someone "asking Jesus into his heart", or someone "praying the sinner's prayer". or someone "walking an aisle", or praying to God for forgiveness, etc? If the physically dead are in fact raised solely by God's sovereign will and his bestowal of the gift of life into a dead body, then why would it be any different with the gift of eternal that God freely and sovereignly gives through Jesus to whomever he pleases (1Pet 3:7; Rom 6:23; Jn 5:21)?
When it comes down to brass tacks, the bible seems to use many more similes than "mere" metaphors. The latter is "a figure of speech in which a term or phrase is applied to something to which it is not literally applicable in order to suggest a resemblance". Whereas the former is actually stronger and more accurately depicts what often is going on in scripture:
The comparison of two unlike things! Similes, therefore, have a strong paradoxical sense that attaches to them; for by definition a "simile" is: "a figure of speech comparing two unlike things". And this is precisely what we have going on with the Doctrine (dare I say it at the risk of using a "worldly" word?) of the Resurrection. Physical resurrection consists of raising the seen, physical dead to temporary new life; whereas spiritual resurrection consists of raising the unseen, spiritual dead to new life eternal. And in both cases the Dead contribute nothing, zip, nada, bupkis, to their restored life.
Personally...methinks Augustine was right on! At least he didn't try to perform great feats of mental gymnastics or torture logic or ignore scripture to formulate his understanding of biblical doctrine.