A REPLY TO MY ANSWER
Thank you for that detailed answer, but it's still a little ambiguous. In order to be chosen, do you have to be a Christian, or is simply knowing all the truths of God enough to qualify a person as chosen? Those who only know all the truths, but aren't Christians... can they be said to have tasted of the Heavenly gift and have partaken of the Holy Spirit? You once told me that in order to get either the First or Third Resurrection, a person has to know all the truths of God. However, is Paul saying that in addition to that, these people need to have tasted of the Heavenly gift and partaken of the Holy Spirit as well?
You can know mentally the truths of God, people can sit down to study what is the truth of the matter on a biblical subject, and make it an assignment like studying for an exam.....it's called "head knowledge" - having a good old jigsaw like game, and still with that "technical" correct knowledge, NOT BE A CHRISTIAN!
Then some knowing this, go to the other end of the swinging pendulum, and think knowing the truth of God are contained in the Bible, and knowing head knowledge does not "save" you, they jump on the pendulum heading for "heart emotion" - tingle up the spine, and believe as long as you heart felt emotion kicks in, and living a "good" life [as defined by their "church"] you are already there.
BOTH ideas on Christianity are false !!
You are as written, "Prove all things and hold fast to that which is good." and "Study to make your self approved unto God, a workman that needs not be ashamed, correctly dividing word [getting the pieces to fall into the whole truth on any Bible topic] of truth.
To be a true Christian, one that is over first base, you have to be called to hear God's truth - salvation, the kingdom to come, the conditions to enter the kingdom now --repentance, saving faith, baptism, lay on of hands, receiving the Holly Spirit. When you have been partakers of all this heavenly blessing, the facts of it all and the emotions of it all....the mind and the heart together as one, you are willing to set your mind to love and serve HIM with all you have....... THEN your head and heart are on the right track to, as Jesus said, "Man shall not by bread alone but by every word that proceeds from the mouth of God [Matt. 4:4].
With ONLY head knowledge, many can have that, but it gets them no where with God; you have to have some head knowledge, but more still, with the heart humility God can work with, as you continue your faith, walk down the one straight and narrow path that leads to eternal life.
Those who only know all the truths, but aren't Christians... can they be said to have tasted of the Heavenly gift and have partaken of the Holy Spirit?
NO they cannot be said have tasted of the heavenly gift and partakers of the Holy Spirit. They may have no more than taken the first step up to the batters box, but that's about it. Not until there is a heart felt, personal relationship, with the Father and with Jesus the Messiah, can someone be considered a true disciple of God and have enjoyed having all the heavily gifts, and Holy Spirit He wants to give you.
Yes Paul is talking about real true Christians here, who have gone so far as to have enjoyed the the heavenly gifts and as also having the Holy Spirit sometime, in their lives.
So Paul is talking about real true Christians falling back, their connection with heaven has stopped. They've gone back to the society of the world they came out of.
This section here is akin to the section in chapter 10 of Hebrews.
Bottom line.... only God knows if a person has committed the "unpardonable" sin; which we've given space in answering that often asked question, on this website.