Does the verse Luke 9:62And Jesus said unto him, No man, having put his hand to the plough, and looking back, is fit for the kingdom of God.
See All... talk about backsliders in the tense of they were never saved?

Luke 9:62And Jesus said unto him, No man, having put his hand to the plough, and looking back, is fit for the kingdom of God.
See All... states, "And Jesus said unto him, No man, having put his hand to the plough, and looking back, is fit for the kingdom of God."

Though the emphasis here seems to be on discipleship, the phrase about not being fir for the kingdom of God may put it in a different light. The New Testament deals with a class of people that is often ignored today.  These are the people who seem to believe but quickly and permanently return to their old ways. The Bible teaches that these people were probably never saved.

1 John 2:19They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us.
See All... states, "They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us." This verse is very clear. There are some who identify the absence of true faith in their lives by their ability to go back to the world.  2 Peter 2:20-22 [20] For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning. [21] For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them. [22] But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in the mire.
See All... compares them to a sow that returns to the mire; or, as we might say, the pig returns to the pig pen. But notice, the pig never became a sheep--it was still a pig. It just acted like a sheep for a period of time.

This is not to say that all backsliders are false professors of the faith. True backsliding can be done only by those who have truly gone forward. In other words, a backslider is someone who truly knows God.  Yet, God tells us that a child of His is always His child and will be treated as His child. This means that a true child of God who backslides will be chastened as a child. God will scourge every son He receives (Hebrews 12:6For whom the Lord loveth he chasteneth, and scourgeth every son whom he receiveth.
See All...). He who does not receive chastisement is not a true son, but is illegitimate (Hebrews 12:8But if ye be without chastisement, whereof all are partakers, then are ye bastards, and not sons.
See All...).

How can we tell whether someone is backslidden or if he is not a true believer? We cannot always tell. However, I see two indications of true belief in one who has gone away from the Lord. First, he does not get away with it. That is, God will chasten him in order to bring him back to Himself. Second, he retains a desire to get right with God in his heart.  aul talked about this desire to do right even though he kept doing wrong in practice (Romans 7:15-25 [15] For that which I do I allow not: for what I would, that do I not; but what I hate, that do I. [16] If then I do that which I would not, I consent unto the law that it is good. [17] Now then it is no more I that do it, but sin that dwelleth in me. [18] For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not. [19] For the good that I would I do not: but the evil which I would not, that I do. [20] Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me. [21] I find then a law, that, when I would do good, evil is present with me. [22] For I delight in the law of God after the inward man: [23] But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members. [24] O wretched man that I am! who shall deliver me from the body of this death? [25] I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.
See All...). This will be the experience of true believers who get away from God. They will never have the same enjoyment of sin that they once had. They will deal with greater guilt than before and will have greater internal struggles. The Spirit of the Lord is in them and they cannot go back to "business as usual" in the world.