The acronym SIN could stand for many things. Here are three that beget the next and necessitate a fourth: Satanically Initiated Nonconformity; Selfish In Nature: Steeped In Nihilism; because of these Salvation Is Necessary. Most of us associate the word sin with particular activities that used to be unacceptable in society. However, the definition of sin has changed with the passage of time, and most are unaware of the true definition of and ramifications of sin. The simplest definition for sin is: Doing things ‘not’ God’s way, and the cost is death. 
Long ago, the first sin was committed when Satan began to believe he was more than he was created to be (Is 14:13-14). He became lifted up in pride and decided he would not only rebel against God, his Creator; he would lead a rebellion that would enthrone him as god. According to Scripture, his plan actually worked. He did, in fact, lead a third of the angels into insubordination along with all of humanity. Therefore, when employed, ‘Satanically Initiated Nonconformity’ was very successful, and Satan achieved his goal; he became god of this world. He accomplished this by creating an atmosphere of rebellion, where sin abounds. 
Mankind naturally became ‘Selfish In Nature‘ once the idea that they could be as God was accepted. This selfishness is arguably the root cause of so many ailments, both spiritual and physical. This is because God blesses those who choose his will over their own, and he turns those who reject him over to their own lordship, a job title they are woefully unqualified for:
“But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him.” 
“For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness; Because that which may be known of God is manifest in them; for God hath shewed it unto them. For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse: Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened. Professing themselves to be wise, they became fools, And changed the glory of the uncorruptible God into an image made like to corruptible man, and to birds, and fourfooted beasts, and creeping things.
“Wherefore God also gave them up to uncleanness through the lusts of their own hearts, to dishonour their own bodies between themselves: Who changed the truth of God into a lie, and worshipped and served the creature more than the Creator, who is blessed for ever. Amen.”
Once selfishness has taken root, the next step in the process invariably manifests. The non-believer becomes ‘Steeped In Nihilism,’ which is what eventually happens to men who continually reject God’s authority. You see, nihilism can be defined as a total rejection of all established authority and institutions, and the word steeped means one is fully engrossed in something. In this case, the sinner is completely beholden to a lifestyle that rejects God’s authority. This is a bad news-good news situation. Here is why:
My momma used to say, “Sometimes the Lord has to get you flat on your back to get you to look up.” This is exactly what God does to those who reject Him. He simply shows them their condition. He does this by turning them over to reprobate minds, which causes them to do inconvenient things, which hopefully, after a season, become loathsome (Rom 1:28). This is why the Word tells us that sin loses its savor after a season (Heb 11:25). God is trying to cause the sinner, through experiencing the consequences of ‘bad’ choices, to realize they have need of a Savior, the ‘good’ choice.
“For when ye were the servants of sin [Steeped In Nihilism], ye were free from righteousness. What fruit had ye then in those things whereof ye are now ashamed? for the end of those things is death [This is the bad news]. But now being made free from sin, and become servants to God, ye have your fruit unto holiness, and the end everlasting life. For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord” [This is the good news]. emphasis mine – author’s comments bracketed
This is where the fourth and most important use of the acronym SIN comes in. Because of the sin involved in the first three steps in the process, “Salvation Is Necessary.” This is because man is incapable of saving himself. In fact, as we have seen, he will, without divine intervention, continue in sin to the point of eternal damnation, a condition which is absolutely in the future for those who continue to reject God’s free gift of Salvation:
“And whosoever was not found written in the book of life was cast into the lake of fire.”
Sin is far worse than any cancer known to man. In fact, sin is far more invasive; it literally permeates the soul of those ruled by it. However, taking a look at cancer may be a good way to describe how sin gains a foothold, grows, and eventually kills the one infected with it. According to the National Cancer Institute, Cancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body.  Sin follows this same pattern.
Every person has cells, and according to Scripture, all have sinned (Rom 3:23). Therefore, sin is already present in each individual. And this sin, without fail, will begin to grow uncontrollably until it overwhelms the whole person and, without treatment, kills the sinner (Rom 6:23). The good news is, like cancer, sin is treatable. All one needs to do is recognize and confess their sinfulness and believe that Jesus – the perfect sacrifice which was validated by His resurrection since death could not hold Him (Acts 2:24; Rom 10:9) – already paid the price for all who trust in His sacrifice (Rom 5:8). In fact, through faith in Christ, sin can be removed as far as the east is from the west (Ps 103:12) and replaced with the righteousness of God through Christ Jesus (2 Cor 5:21).
However, like with cancer, once one has been diagnosed with a sin condition and healed of it, they must forever remain on guard because it will attempt to regain its former foothold. This is why the Apostle Paul spoke of the Christian walk as a fight of faith which one must remain faithful in until death or the rapture (1 Tim 6:12; 2 Tim 6:7).  He understood that believers must mortify the deeds of the flesh until Christ returns. Paul explains:
“If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God. Set your affection on things above, not on things on the earth. For ye are dead, and your life is hid with Christ in God. When Christ, who is our life, shall appear, then shall ye also appear with him in glory.
“Mortify therefore your members which are upon the earth; fornication, uncleanness, inordinate affection, evil concupiscence, and covetousness, which is idolatry: For which things’ sake the wrath of God cometh on the children of disobedience: In the which ye also walked some time, when ye lived in them. But now ye also put off all these; anger, wrath, malice, blasphemy, filthy communication out of your mouth. Lie not one to another, seeing that ye have put off the old man with his deeds; And have put on the new man, which is renewed in knowledge after the image of him that created him: Where there is neither Greek nor Jew, circumcision nor uncircumcision, Barbarian, Scythian, bond nor free: but Christ is all, and in all.”
Paul is encouraging the believer to remain faithful to God until Christ appears. The reason this is so important is the fact that sin is essentially choosing anything over God. In other words, all that takes preeminence over God is sin. Think about this for a moment in the following context: Anything that becomes more important than God in our lives is sin. Now consider all of the things which vie for your attention these days…
During this moment of reflection, did you find some things that have become more important to you than God? If so, mortification is in order. Yes, Christ paid the price for all of our sins; however, we must continue to mortify our members until they no longer remain on earth. The good news is, God has provided a way for us if, while we wait, we find sin in our lives. The Apostle John can help us here:
1 John 1:5-10
“If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.” emphasis mine
One final point about dealing with sin while we await the bridegroom. Scripture makes it clear that we can live here on earth in a state of peace, even with the current state of affairs. In fact, Isaiah assured us of this when he said this about God: “Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee” (Is 26:3). This simple verse is the antidote to the sin problem of man; in it, man places God in the correct position, He is preeminent, and man’s mind is stayed (fixed) on the Lord.  From this place, God can and does bless the faithful. But how do we maintain this attitude indefinitely? The Apostle Paul tells us:
“There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit. For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death. For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh: That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit. For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit.
“For to be carnally minded is death; but to be spiritually minded is life and peace. Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be. So then they that are in the flesh cannot please God. But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his. And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness. But if the Spirit of him that raised up Jesus from the dead dwell in you, he that raised up Christ from the dead shall also quicken your mortal bodies by his Spirit that dwelleth in you.
“Therefore, brethren, we are debtors, not to the flesh, to live after the flesh. For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live. For as many as are led by the Spirit of God, they are the sons of God.”
SIN begins with believing the lie that one can be as God. It then festers into overwhelming selfishness, which metastasizes into the rejection of all outside authority. When one reaches this point, they have, in their own minds, become god. At this point, it is very difficult to renounce godhood and turn to the true God. Perhaps this is why Jesus said it was hard for a rich man to enter into the kingdom of heaven (Matt 19:23). After all, if one has no need of one higher than himself, why should he ever call out to God?
As believers, we must set our minds on heavenly things and, through the Spirit, mortify the things of our flesh which make it difficult to do so. Until our last breath, we must remain vigilant against the cancer of sin. Indeed, at the first sign of a problem, we must purge the errant from our systems. After all, when cancer is diagnosed, it must be treated with medicine; and when successful, the patient is declared to be cancer-free. When sin shows its ugly head, it must be treated with truth. And when God’s Word is properly applied, and through the Spirit, the deeds of the body are mortified, the recipient is declared free indeed.
“And ye shall know the truth, and the truth shall make you free.”
“If the Son therefore shall make you free, ye shall be free indeed.”
Website: In His Commission
 For greater understanding, see the article, “The Man of Sin Arising.”
 For greater understanding, see the article, “The Greatest Lie Ever Told: The Origin of all Lies.”
 “Unless otherwise noted, all biblical passages referenced are in the King James Version.”
 For greater understanding, see “National Cancer Institute.”
 If you missed the rapture, see this article, “Open Letter to Those Who Miss the Rapture.”
 For greater understanding, see the article, “Big God – Little Man.”