We have discussed how the Sinful Nature was not part of God's original creation, but was acquired as an add-on attachment to the human soul when Adam and Eve sinned. Saying it is "attached" to the soul means the Sinful Nature is much like a barnacle on the hull of a ship, or a leach on a person. It was not meant to be there. God did not create it or design it. It was a human "creation" of the man and woman when they first sinned and revolted against God. Rejecting God had enormous consequences not just for the original man and woman, but for all who would be descended from them. The long term effects of that one act of disobedience has been monumental, and will result in eternal misery for many. God held Adam directly responsible for the original sin, because Eve was deceived into it, but Adam chose deliberately with full knowledge of his actions. Therefore it was Adam who chose sin and gained a Sinful Nature for all humans, and that Sinful Nature was passed down through Adam to his offspring. It is attached to the soul of every human when they are born except for Jesus Christ, who was not conceived from a male descendant of Adam, which avoided Adam's sinful legacy from being handed down to Him since He was not from Adam, but rather was "the seed of the woman." (Genesis 3:15) That is the significance of the virgin birth, that Adam's legacy had no effect on Him.
The Sinful Nature is what tempts humans to disobey God, to revolt, to misbehave, to be arrogant, to disregard the normal functions of the soul and instead act irresponsibly. It is more instinctive and animalistic than the soul was intended to be as designed by God. And it is also the legacy of the revolt of Satan against God. When Satan sinned against God, and also the angels who joined him, each of them acquired a similar Sinful Nature at that point. So the Sinful Nature actually pre-dates humans, since it is an ancient legacy of the revolt of Satan. And Satan tempted the first humans into sin in order to pull them toward himself and away from God, therefore humans were lured through arrogance into accepting the Sinful Nature just as Satan had. The Sinful Nature is what makes all who have it sin and disobey God in all the many ways creatures do so. It is indeed the enemy within each of us.
The fact that the soul is the source of so many negatives also proves that the Sinful Nature is attached to the soul, even though not inside the soul. The Sinful Nature is that part of the soul which Satan "owns" since he was the source of its creation at the fall of man. So the Sinful Nature is how Satan's Cosmic System influences people, and this is true whether it is a believer or unbeliever. Genesis 8:21 says “every inclination of the human heart is evil from childhood.” This is because every person is born under the control and influence of the Sinful Nature. And as the person grows up mentally as a human being, the Sinful Nature develops faster than the soul's logical advisors, and this is especially evident during the teen years. Therefore human "mental growth" is less about brain development than soul development, since soul development is the only way to develop the logical advisors of the soul in a way which opposes the Sinful Nature's influences on the Heart of the soul. This is the battle as a person grows up to human maturity, for unbelievers as well as believers, as the human soul fights to gain logical advantages primarily in the Conscience over the Sinful Nature in order to keep the Sinful Nature under control to some degree. And illogical thinking and actions come from the soul, not from the human brain.
The Bible refers to the Sinful Nature in several ways. Although the phrase "sin nature" is sometimes found, the primary word used is "flesh," as something which was not originally part of the soul, and this is also where the phrase "fleshly desires" originated. The word "sin" in the singular and "sinful" are also used for the Sinful Nature, as well as several other terms. The following Bible verses refer to the Sinful Nature, and they are provided so the Reader can understand more about the Sinful Nature by reading through them without additional commentary. There are quite a few of them, but this is an important issue to understand since it is about the enemy of the soul. (Note: the bolded items are references to the Sinful Nature):
Romans 7:22-25
"For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate. Now if I do what I do not want, I agree with the law, that it is good. So now it is no longer I who do it, but sin that dwells within me."
1 Cor. 3:11–15
"Whatever is done in the power of the sin nature, is “wood, hay, and straw” and has no lasting value."
1 Pet. 2:11
“Beloved, I beg you as sojourners and pilgrims, abstain from fleshly lusts which war against the soul.”
Galatians 5:17
"For the desires of the flesh are against the spirit, and the desires of the spirit are against the flesh, for these are opposed to each other, to keep you from doing the things you want to do."
Ephesians 2:3
"Among whom we all once lived in the passions of our flesh, carrying out the desires of the body and the mind, and were by nature children of wrath, like the rest of mankind."
Galatians 5:16
"But I say, walk by the spirit, and you will not gratify the desires of the flesh."
Ephesians 4:22
"To put off your old self, which belongs to your former manner of life and is corrupt through deceitful desires"
Galatians 5:19-23
"Now the works of the flesh are evident..."
Romans 8:3
"For God has done what the law, weakened by the flesh, could not do."
John 3:6
"That which is born of the flesh is flesh, and that which is born of the Spirit is spirit."
Romans 13:14
"...make no provision for the flesh, to gratify its desires."
Romans 8:3
"For those who live according to the flesh set their minds on the things of the flesh, but those who live according to the Spirit set their minds on the things of the Spirit."
Romans 8:7-8
"For the mind that is set on the flesh is hostile to God, for it does not submit to God's law; indeed, it cannot. Those who are in the flesh cannot please God."
Colossians 3:9
"Do not lie to one another, seeing that you have put off the old self with its practices"
2 Peter 2:18
"For, speaking loud boasts of folly, they entice by sensual passions of the flesh those who are barely escaping from those who live in error."
We can see from the above verses that the Sinful Nature is discussed often in the Bible. With the Sinful Nature attached to the soul, it influences the person in multiple ways, all negative. The term "base instincts" applies to the low level conniving, arrogant, and immoral influences which are promoted from the Sinful Nature. Its primary path is to use the Emotion of the soul to influence the Mind and Heart, since the Emotion is a non-thinking responder to the Mind and Heart. The Emotion of the soul is used because what the Sinful Nature proposes is not truth or moral or even logical. Instead, the Sinful Nature peddles instinctive gratification of lust, arrogance, and other base desires, which entices the Emotion into a relationship with it, if the Heart is not diligent in preventing such an alliance.
Therefore the Sinful Nature works primarily through a system of arrogance and lusts. The arrogance part lures the person into thinking of themselves in vastly superior terms, far above reality. Arrogance therefore becomes a primary means of rejecting that which does not come from self, since only self matters, and only self is all-knowing. The second part, the lusts, take many forms, and are not always the carnal or lascivious type as most think of them. Lusts can be carnal, but more likely, and more destructive, are the lusts for power, wealth, status, superiority over others, and even self-righteousness regarding types of sins. It may seem odd, but the Sinful Nature of each person has unique preferred sins and also non-preferred sins. Each Sinful Nature is different. This is because certain types of sins do not line up with the particular lusts the individual prefers, which the Sinful Nature has acquired along the way. It may also come as a surprise that people who look down on others for the sins they commit, because they are "less refined" than their own sins, are fulfilling a lust for superiority from the Sinful Nature. Whenever another person is regarded as a lesser human than self, the Sinful Nature is exercising its lust to be superior in its own view. This often leads to sins of the tongue against another person. James 3:6 says "The tongue also is a fire, a world of evil among the parts of the body. It corrupts the whole body, sets the whole course of one’s life on fire, and is itself set on fire by hell." The reference to "hell" refers to the Sinful Nature as being a part of Satan's domain, since he is its originator.
The various lusts motivate behaviors which are counter to the plan of God, and interfere with the normal function of the soul as God designed it. And most people have conflicting lusts since the Sinful Nature is not logical, but rather is instinctive. Recall that God did not give humans instincts to live by, but when humans sinned against God they chose instincts, which were introduced into the soul through the Sinful Nature. These lusts are what makes humans instinctive and even animalistic although God did not design humans to function that way. God designed us to think in the soul, not to live by instincts.
The Sinful Nature cannot act on its own and requires that the Heart validate its desires. At first this is not an easy task for the Sinful Nature, and treachery is required. If the Sinful Nature makes progress in getting its way, the process becomes much easier. If this continues, the Sinful Nature can even stage a successful coup against the Heart, whereby the Heart essentially becomes the hostage of the Sinful Nature. The Heart cannot shift the blame to the other parts of the soul and say "it wasn't me who did that" when it gives in to the desires of the Sinful Nature. Usually the Emotion is involved with the Sinful Nature, and the Heart finds it difficult to refuse the Emotion, because the Emotion provides the Heart with feelings such as joy and elation, which the Heart enjoys. The Sinful Nature abuses this relationship between Heart and Emotion to its advantage, and presents its lusts first to the Emotion, and in turn the Emotion presents them to the Heart in the form of enticing emotional fulfillment. These base instincts are from the Sinful Nature, but it is the Heart which must approve them to be released from the soul, therefore the Heart must first validate the inputs from the Sinful Nature/Emotion and make the final decision before any desires from the Sinful Nature are executed as a decision. But the more the Heart gives in to the desires of the Sinful Nature, the easier it is for that Sinful Nature to have its desires approved by the Heart. Over time the base desires essentially become instinctive. When this happens, the Heart becomes hardened into a position of evil as it becomes instinctively predisposed to accept the desires of the Sinful Nature as the policy of the soul. Of course, it does not need to be that way. The Heart can heed the advice of the Mind and its Conscience and reject the overtures of the Sinful Nature. And we will see that when the human spirit is filled with the Word of God, the human spirit can be the most powerful opponent of the Sinful Nature.
Therefore the Sinful Nature is the enemy within, attached to our soul, working constantly to distract, derail, pull us in the wrong directions, cause emotional reactions against right actions, and lure us into revolting against the plan God has for our life. These mental sins become both inwardly destructive and also harmful toward others, including outward expressions as sins of the tongue. For believers the relationship with the Sinful Nature ends at the point of physical death when it is removed from us like a barnacle from the ship hull, or a leach on the skin, and it is gone from us forever. But for unbelievers it will remain part of them eternally, and will increase their torment.
Proverbs 4:22 says "Above all else, guard your heart, for everything you do flows from it." The "guarding" refers to the attacks from the Sinful Nature, which is an illegitimate advisor to the Heart, and is the source of temptations which attempt to get the Heart to decide in favor of things the Heart knows to be wrong, or should know to be wrong. When the Heart is primarily listening to and heeding the advice of the Sinful Nature the soul is working contrary to the design of God. The Sinful Nature is the ally of Satan, and allowing it to control the soul is a particularly disastrous state for believers. It keeps the believer out of the will of God unless it is reversed.
As believers there is a constant war in our soul. It is the battle of good versus evil. Our spiritual side, the human spirit, wars against the Sinful Nature, and vice versa. In most believers, unfortunately the Sinful Nature wins on a more regular basis. It is a sad fact. But for those who seek to please God during their time on earth, they will study the Word of God and fill their human spirit with spiritual learning, and will grow in the knowledge of God. As this growth continues, the believer has greater ability to resist the Sinful Nature and to fulfill the plan of God. They will not be perfect while alive on earth, and the Sinful Nature often gains certain advantages from time to time, but the key is to keep moving forward and continue growing in the Word in order to fill the human spirit with as much knowledge of truth as possible. This provides power from the human spirit to influence the soul's Mind and Heart to follow the will of God and resist the Sinful Nature. That is the primary purpose of the life of the believer after salvation. We believers remain on earth to grow spiritually, to live out of our human spirit which influences the soul to make the right choices, and to defeat the Sinful Nature in our daily walk through life. This is what allows us to love God, appreciate our Savior Jesus Christ, and generally to live as He wants us to live. Then eternity is full of rewards for such a believer.
For unbelievers, if they are controlled by the Sinful Nature they are in a state of revolt against the natural laws which God set in place for all humans to live by and under. The unbeliever can live with their soul working rather normally, the Mind figuring things out rationally, the Heart listening to the advice of the Mind and its Conscience, the Emotion appreciating the experiences the soul enjoys, and that unbeliever can generally live a moral life, being a good citizen, helping their fellow humans in time of need, and being an overall decent person. They are still unsaved, but their life is generally "normal" and stable to a certain degree, even though apart from God. That is the gift God has given them while they are alive, respecting their choice to refuse salvation. But after their short life is over their eternity is a very different matter, since unbelievers will retain their Sinful Nature and all its negative motivations for all eternity, as the Bible says, they will have anguish, regrets, anger, remorse, fears, weeping and all manner of negative thoughts which will make them even more miserable. The believer will have none of these. But for the unbeliever the Sinful Nature will be a secondary source of soul pain during eternity, along with the intense physical pain. Unbelievers will live eternally with the same soul they had while alive, including their Sinful Nature, but they will never have a human spirit.
And speaking of the human spirit, it is finally time to take a more detailed look at this component of the inner human which is only found in believers. It is what makes humans a spiritual being capable of interfacing with God.