During a small and informal Bible study today, a question arose out of Romans 7, specifically from verses 15-20:
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. For I know that nothing good dwells in me, that is, in my flesh. For I have the desire to do what is right, but not the ability to carry it out. For I do not do the good I want, but the evil I do not want is what I keep on doing. Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me.
The dispute was about the "sin nature" and whether it is displaced by the regenerative act, or remains alongside the "new man."
I mistakenly believed Aron was going down the route of perfectionism or other theologies that argue that man is capable of moral perfection in thought and deed, and in this life. I reflexively took the position that we remain with our sin natures, as evidenced by the continuing presence of sin in our lives. I apologize for my misunderstanding, and emphatically reverse my position. It will be useful to consider a few things in reaching this conclusion.
The Scriptures on the New Man
The Bible teaches throughout that the essence of salvation is the unilateral action of God in imparting to us a new nature.
Our old nature is death. Paul calls us "dead in our trespasses" (Eph 2:5) and "dead in our sins" under the law (Col 2:13). God promised Adam and Eve that on the day they ate of the fruit of the tree of the knowledge of good and evil, they would surely die. Our old nature is rebellion and self-worship, or at least not-God-worship. We are, in our hearts, idolaters. We are hopelessly enslaved to sin because of our natures. Our Lord Himself reveals this slavery in no uncertain terms in His discourse in John 8:31-57, culminating in His dramatic declaration of His deity. Paul reinforces the point in Romans 6, pointing out the mutually exclusive masters especially in verses 16 and 20. The moment that our first parents sinned in the garden, our natures were torn from the benevolent mastery of our God and shackled to the cruel master of self-worship. This, in my considerably modest opinion, is what it means to be spiritually dead.
I have been developing a general thesis in my mind for some time regarding the use of the word ζωὴ for spiritual life and the word βίος for physical life. It seems that once the ζωὴ ended in the garden, the dependent βίος followed as a matter of course. Likewise, in order for our βίος to be properly restored, God embarked on a program to resurrect the ζωὴ.
So our old natures were spiritual death, which is separation from God, which is enslavement to sin and takes the form of worship of self.
My amateur ramblings aside, we know that the wages of sin are death (Romans 6:23) and in so defeating death Jesus took away sin's power. Sin has become a toothless enemy in the face of the accomplishment of the cross, our adversary unable to wield his only weapon: "Since therefore the children share in flesh and blood, he himself likewise partook of the same things, that through death he might destroy the one who has the power of death, that is, the devil" (Hebrews 2:14). So the manner by which God undertook to destroy our enemy was to join is in our humble estate, emptying Himself of glory, discarding His divine perogative, and subjecting Himself to the apex of humility, death at the hands of an unworthy rabble and usurpers to His true authority (huamns generally, the Jews in the ecclesiastical realm, and the Romans in the civil realm).
One of the early memory verses in the Topical Memory System is Galatians 2:20, "I have been crucified with Christ. It is no longer I who live, but Christ who lives in me. And the life I now live in the flesh I live by faith in the Son of God, who loved me and gave himself for me." This verse is certainly under the umbrella of "the mystery of the faith" (1 Timothy 3:16). It invites deep reflection on what John Owen called "The Death of Death in the Death of Christ"- the profound and central triumph of the Cross.
And so we arrive at the most profound of all the mysteries: that by His death, Christ has brought us in to participate in the eternally-ancient covenant relationship that is the Trinity. This is nowhere more profoundly and terrifyingly declared than by Jesus on the night before His death: I in them and you in me (John 17:23). In destroying death, He fulfilled the prophecy "When he ascended up on high, he led captivity captive" (Eph 4:8, quoting Psalm 68:18).
Bringing it back to our discussion of natures, the Lord also fulfilled the prophesy of Ezekiel: "And I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh." (Ezekiel 36:26). This is what Jesus meant when He told Nicodemus that he had to be born from above. Regeneration is from God, from start to finish, and the means - the only means - by which God accomplishes this plan of redemption is by giving man a new nature to replace the old.
So we can say with Paul that we put off the old man (Eph 4:22), and most blessedly with Peter that we have been made partakers of the divine nature! (2 Peter 1:4).
One can and likely will go on for all eternity about the beauties of this mystery. Suffice it to say that without a transplant of the old nature, there is no salvation.
As a final note, we encounter a semantical problem when discussing natures. As we usually mean it in these contexts, nature means "heart" as Ezekiel meant it. We mean our basic allegiances, or that to which our will is bound, to paraphrase Luther. When our wills are bound to sin, we are essentially sinful. When our wills are freed from sin and bound to God, we are essentially holy. This, of course, is just another way of expressing the mystery above, but it helps clarify the terms.
The term "dual nature" has historically conjured the question of the nature of Jesus Christ. The Arian heresy treated Jesus as a mere man, Nestorians argued that His two natures were always separate so He was kind of like a machine with two processors (or something), and various other heresies denied one or other aspect of the God-Man formulation. Historic Christianity, that is to say, accepted orthodox belief (at least from Chalcedon), has always taught that Jesus Christ was completely human, completely divine, and one person. This is a mystery that is as profound as the incarnation, but it is essential to the atonement.
So I propose the term "nature" be reserved for our humanness, and instead we talk about being reborn or regenerated as a new man or new self. This is both clearer and tracks better with the language of Scripture.
This presents a rather obvious question: why do believers still sin? It is this question which has led many genuine believers and heartfelt evangelicals to conclude that we must struggle with dual and competing natures until this life should end. But this is the answer based on man's reasoning and not on the Scriptures. So what does God say about this subject?
John tells us in his first epistle that everyone still sins, that the man who claims he has no sin makes both himself and God a liar. This is a rather dangerous perdicament in which to find oneself, and so we should proceed with great care.
There is a degree to which the Bible gives us indications that persistent and unaddressed sin is a sign of unbelief. Allow me to disclaim here that I do not think it is the general busienss of Christians to assess the veracity of the beliefs of others. It is, however, the gospel business of the gospel church to see that members are in the faith and that false-converts or the merely confused are addressed. So we see in 1 John 2 vv19-26 that the later actions of some expose them as unbelievers all along. This squarely defeats the charge of some that "falling away" of once-professing believers indicates that salvation is tenuous and can be lost. God forbid - Salvation is of the Lord, and God never fails!
But we are given great hope. We will struggle with the remnants of our sinful flesh so long as we inhabit these bodies. Indeed, this is the great promise of the glory we are to experience in new bodies (Phil 3:20-21, cf Job 19:25). But the Lord has sent us His paraclete, the Holy Spirit, to aid us in all things Spiritual, to intercede for us in prayer, and to guide is and enable us with the grace that comes only from God. God also promises us that "No temptation has overtaken you that is not common to man. God is faithful, and he will not let you be tempted beyond your ability, but with the temptation he will also provide the way of escape, that you may be able to endure it." (1 Cor 10:13)
For brevity's sake, I will leave off addressing the rest of the aspects of dealing with sin in this life. It will have to be sufficient for this post that the Scriptures tell us we are not free from sin in this life, and they tell us this unequivocally. The application is to appeal to the Spirit, to God, to root out this sin and to conform you to the likeness of His Son, which He has promised to do (see Romans 8:29ff and others). You can always rely on God to keep His promises.
So we see in the Scriptures that we are given a new heart (or that we are reborn) in God's magnificent program of working out our redemption in history. We also know that this is the basis for our complete justification, that in putting on Christ we have put off the old, and that it is on His merit alone that we can approach God and commune with Him.
We also know that we are not free of sin in this life. It is preposterous to assume that man has two natures and that we are some kind of superintending intelligence presiding over conflicting tendencies. We have but one nature, human, and our hearts, our basic allegiances, can either be to He who deserves it, or it can lie in not-Him. There is no third way.