1. "Will a believer be saved, no matter into what course of sin he may fall, and die in?" A true believer will, infallibly, be saved; but we consider that salvation includes, not only full deliverance from the future consequences of sin, but from the present power and practice thereof. And, hence, if we find a person living in sin, and yet talking about his assurance of salvation, we look upon him as an antinomian, and not a saved person at all. "If we say that we have fellowship with Him, and walk in darkness, we lie, and do not the truth." The believer may fall, but He will be lifted up; he may be overtaken, but he will be restored; he may wander, but he will be brought back, because Christ is able to save to the uttermost, and not one of His little ones shall perish.
2. "Will the Holy Spirit dwell in a heart where evil and unholy thoughts are _indulged_?" The body of the believer is the temple of the Holy Ghost. (1 Cor. vi. 19.) And this precious truth is the ground of exhortation to purity and holiness of heart and life. We are exhorted not to grieve the Holy Spirit. To "_indulge_" evil and unholy thoughts is not christian walk at all. The Christian may be assaulted, grieved, and harassed by evil thoughts, and in such a case he has only to look to Christ for victory. Proper christian walk is thus expressed in John's first epistle: "We know that whosoever is born of God sinneth not; but he that is begotten of God keepeth himself, and that wicked one toucheth him not." (Chap. v. 18.) This is the divine side of the question. Alas! we know there is the human side likewise; but we judge the human side by the divine. We do not lower the divine to meet the human, but ever aim at the divine notwithstanding the human. We should never be satisfied with anything lower than 1 John v. 18. It is by keeping up the true standard that we may expect to raise our moral tone. To talk of having the Spirit and yet "_indulge_" in evil and unholy thoughts is, in our judgment, the ancient Nicolaitanism (Rev. ii. 6, 15), or modern antinomianism.
3. "If it be so, then, will not people say, they may live as they like?" Well, how does a true Christian like to live? As like Christ as possible. If one had put this question to Paul, what would have been his answer? 2 Cor. v. 14, 15, and Phil. iii. 7-14, furnish the reply. It is to be feared that the persons who ask such questions know but little of Christ. We can quite understand a person getting entangled in the meshes of a one-sided theological system and being perplexed by the conflicting dogmas of systematic divinity; but we believe that the man who draws a plea from the freedom, sovereignty, and eternal stability of the grace of God to continue in sin, knows nothing of Christianity at all, has neither part nor lot in the matter, but is in a truly awful and dangerous condition.
As to the case which you adduce, of a young man who heard a minister state in his sermon that "once a child, always a child," and who took occasion from that to plunge into and continue in open sin, it is only one of thousands. We believe the minister was right in what he said, but the young man was wrong in what he did. To judge the words of the former by the acts of the latter is utterly false. What should I think of my son, if he were to say, Once a son, always a son, and therefore I may proceed to smash my father's windows and do all sorts of mischief? We judge the minister's statement by the Word of God, and pronounce it true. We judge the young man's conduct by the same rule, and pronounce it false. The matter is quite simple. We have no reason to believe that the unhappy young man ever really tasted the true grace of God; for if he had, he would love and cultivate and exhibit holiness. The Christian has to struggle with sin; but _struggling_ with it and _wallowing_ in it are two totally different ideas. In the one case we can count on Christ's sympathy and grace; in the other, we are actually blaspheming His name by implying that He is the minister of sin.