The apostle Paul says that the law of sin dwells “in [our] members” (Rom. 7:23) and further exhorts us not to let it reign in our mortal bodies (Rom. 6:12), suggesting that it is present there. If the principle of sin remains with us, and the term sin nature refers to this principle, then how can anyone maintain that Christians by coming to Christ no longer have a sin nature?
As Christians we can get into theological trouble because of inadequate understanding of what the term nature means. Nature here refers to one’s disposition, inclination, or bent — the principle or law that governs one’s behavior. When Christians believe that “no person can consistently behave in a way that is inconsistent with how he perceives himself,” we fail to recognize that it is not one’s self-perception but rather one’s nature with which one cannot behave inconsistently. If Christians had only a Christlike nature they could only behave like Christ.
The reason Christians are capable of both righteousness and sin is that they have two natures from which to draw. Now, there is another, larger sense in which the term nature is used that refers to an entity’s collection of defining attributes. In this sense, all human beings have only one nature that includes one moral faculty that is capable of both good and evil. Using the narrower sense of the term nature (disposition determined by principle or law), this moral faculty takes the form of the sin nature when it is governed by evil and the new nature when it is governed by good.
In addition to the orientation around the interests of self that all mortals possess, Christians are given an additional orientation around the interests of God. The new orientation inclines us toward good and thus wages war with our original orientation, which inclines us toward evil. The New Testament clearly describes Christians in a state of inner conflict in which they must deny one set of natural inclinations or the other (see Gal. 5:16–17; Rom. 7:15–25; James 4:1–3; 1 Pet. 2:11).
It isn’t as though Christians start out with three-fourths of the original nature and one-fourth of the new and must work to decrease and increase the respective percentages. The old nature is still there in its full strength and ugliness — but we are no longer slaves to it. We can and must choose daily which orientation we are going to “clothe” ourselves with or “put on” (Rom. 13:14; Eph. 4:22–24; Col 3:1–14). Sanctification consists of increasingly learning to live according to the new capacity, which is accomplished as the Word of God is applied to every area of one’s life2 (e.g., Ps. 119:11, 105; James 1:22–27; Heb. 4:2; 5:12–14; 1 John 2:4–5).
The Bible calls the old nature sin or the flesh. The new nature is referred to as the spirit, and the individual as determined by these natures is identified either as the old man (self: NIV, NASB) or the new man. The spirit is the moral nature of Christ, just as the flesh is the moral nature of Adam after the fall that he passed on to his descendants. Christ is the second man, the last Adam (1 Cor. 15:42–50). All human beings are identified with Adam by birth and thus do by nature the things that Adam would do. Those who are identified with Christ by faith and second birth have transferred from the headship of Adam to that of Christ (Rom. 5:12–21), and now, by the indwelling of the Spirit of Christ, have a second nature to do what He would do. In the next world, this will be the only possibility. But in this world, sin remains “in my members.” By this, Scripture is teaching that the very fact of human mortality carries with it not only physical corruptibility, but moral corruptibility as well.
It is because of the spiritual corruptibility that is inseparable from the mortal body that Paul cries, “Who will rescue me from this body of death?” (Rom. 7:24), and that believers, who have the first fruits of the Spirit, “groan inwardly” as they eagerly await the redemption of their bodies from mortality to immortality (Rom. 8:23). As long as we remain in our mortal state we will also remain vulnerable to the tendencies to corruption that define mortality.
Christians who insist that mortal believers no longer have a sin nature is therefore an argument in which its conclusion does not follow from its premises just as the insistence of “faith” teachers that mortal believers should live perfectly free of sickness and physical deterioration.
This inextricable relationship of the sinful nature to our mortal bodies is why Paul calls the sin nature the “flesh.” It is human nature apart from the redeeming influence of the Spirit of God, and thus Paul can say, “I know that nothing good lives in me, that is, in my flesh” (Rom. 7:19). Since sin remains “right there with” every believer (Rom. 7:21), he or she must make a conscious choice to walk according to the new nature and mortify in his or her day-to-day life that which forensically and ultimately was put to death on the cross (Rom. 8:13; Gal. 5:24; Col. 3:5).
1 John 1:8 specifically states, “If we say that we have no sin, we are deceiving ourselves and the truth is not in us.” Note that John speaks of having sin, not committing sin. The term sin in its singular form is frequently used in the New Testament to refer to a principle or law that results in acts of disobedience rather than specific acts of disobedience themselves (John 8:34; Acts 8:23; Rom. 5:12–21; 6:2, 6–7, 10–23; 7:7–27; 8:2; Gal. 3:22; Heb. 12:1, 4).
Some may respond to this observation by arguing, “‘Having’ sin and ‘being’ sin are two totally different concepts.” Indeed, they are. But those who argue that Christians still have a sin nature do not claim that Christians are sin. If Christians were sin they would be incapable of anything but evil. But if they have sin it means that they possess a disposition toward evil that must be counteracted by the new disposition toward good they’ve received in Christ. Only if sinning is rooted in natures they will continue to possess for the rest of their lives does the Apostle John’s statement make sense. If, as some may teach, sin is merely rooted in conditioning that can be changed, it is theoretically possible to stop sinning permanently — which would contradict 1 John 1:8.
The Bible does generally call Christians saints and not sinners (believers are called sinners in 1 Timothy 1:15, James 4:1–9, 5:19–20, and Galatians 2:17) because the term sinner usually connotes someone whose life is characterized by unrepentant sin (e.g., 1 Tim. 1: 9; 1 Pet. 4:18). The apostle John referred to this kind of sin when he affirmed that someone who is born of God does not sin (1 John 3:9). But it is no more unbiblical for us to say we are sinners than it was for Paul in 1 Timothy 1:15,5 for “nothing good lives in me, that is, in my flesh.”