Yes, a person can quench even that little bit of Light, and then he has no hope at all beyond the limits of his natural carnal period of time. I do not believe that this can be done while completely ignorant of the things of God. To reject something of God's, I believe, a person must understand what it is he is rejecting. Only with such recognition can he be in danger of blapheming the Holy Ghost and losing any hope of ever being reconciled with God. The shadow of this is seen in the rejection of King Saul by God. Normally, no one but God and perhaps the individual rejected would be definitely aware that such a rejection had occurred. In the case of Saul, we know from scripture that God told Samuel, so another person can know, but it is not something to be presumed simply because of the terrible place a person is in at the moment. Some of those may still be redeemed.
SUCH an important point! That's well supported by Hebrews 10:[26] "For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins, [27] But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries."
But there are other ways to fall into that predicament. We tend to think along the lines of a mature Christian going back to some terrible social sin, but going back into a contrary religion that denies the biblical savior will qualify a person for that fate. Read on...returning to greater confidence in Moses or some other religious theory such as held by many modern cults despises the blood of Christ after having been a partaker of it.
I've tried to minister to a few men who knew perfectly what that "fearful looking" is about. It's something not recommended for a casual Christian to witness. There is great torment in it, knowing God will have to judge you after having been washed by the blood of Jesus and immune to judgment through faith, then becoming so spiritually "soiled" as to put Jesus to great shame... Paul warned in the end of that chapter not to fall back from faith, meaning a slinking back into "perdition", true apostasy from the faith required to be in Christ. The word "perdition" is equal to "loss" or "ruin". If we truly lose something or it is truly ruined, it is not eligible for recovery.
I think it is important not leave the impression that if a Christian falls back into some sin lifestyle for a season that Heb 10 automatically kicks in forever after. There's a process of knowledge-gaining then of willful rejection of it. Sin itself has been judged in Jesus. He bore the punishment. But to choose to return to serving sin while rejecting the wonderful knowledge of Jesus' salvation, the path leads directly to a rejection by God's provision since salvation is begun in faith, and continued in faith until our last hour in the flesh. One can't live by faith while despising the blood of Christ, or returning to salvation by keeping the law of Moses, or any other religion after having come to a clear knowledge of salvation by faith as provided through Jesus.
That said, the wife of an unbeliever has good reason to follow as best she can the instructions from Paul. One reason for it is if a spouse can't live the Christ way and have any hope in redemption of the other, why bother witnessing to anyone else? I witness to lots of folks, but most insist on somehow discovering how well I live what I preach. That's very important to probably most people. Every disciple that followed Jesus started out as unbelievers, being but somewhat "followers" of Moses, all to their own eternal damnation if left in that state.
It is decidedly best for a Christian not to enter into an unequally yoked relationship. But many have made a bad decision, and now their lives are more complicated, divorce not a good path to follow. The best path is to find solutions and leave open the possibility of all concerned being saved. Paul made it clear that once the unbeliever packs up and leaves, it's over. Don't beg them to stay. But if the unbeliever wants to stay while the other insists on living the Christ Way in the home, then that's probably the ministry one is called to.
A person who is a reprobate knows he or she is a reprobate. They are likely to reveal that in many ways, by action and or word, and on purpose. I have not met anyone who is a reprobate who would tolerate living with a Christian who lives the word.
Edited 11/7....SO,
in my answer to the OP, the Bible gives a great solution for that spouse sharing a house with a reprobate. Godly spouse.....stay on your knees praying for the other, giving yourself over to the WORD of God, saturating your home with dedication to God first, refusing to enter into any sin, in effect becoming unarguably a missionary for Jesus. Don't stay with that evil person if they are abusing you. But if there is no harm, don't be the first to leave over religion. No true reprobate will stick around in the presence of the Holy Spirit and a reborn human spirit in contact with God, and lots of confirmed unbelievers will tend to depart too if the coals are poured on. When they leave, the godly spouse is spiritually released by God even without the case of adultery, free to remarry once the laws of man and of God are met. We might not like some of the laws of men, but we are commanded to obey them, else God will let their law enforcers punish law offenders. Sometimes that is the only path left to a spouse, who must weigh the consequences in remaining true to the law of God in the matter.
As for consequences under the laws of men, I learned a few days ago that a wife who filed for divorce from a man with severe mental problems (and apparently quite reprobate to the point of inability to hold a job anywhere) will remain financially responsible for his care. That's just one example of how important it is to study it all out before being the first to walk out.
Jim