There is much discussion about what the old man-new man, old self-new self, old nature-new nature language means. These terms are Pauline expressions that refer to the contrast between life without Christ and life in union with Christ (Rom. 6:6; Eph. 4:22-24; Col. 3:9-10; cf. a summary of this truth in 1 Cor. 15:45-49). These terms are rich in meaning! But they are also rife for debate and difference of opinion.
David Dockery, “New Nature and Old Nature,” in Dictionary of Paul and His Letters: A Compendium of Contemporary Biblical Scholarship, ed. Gerald F. Hawthorne, Ralph P. Martin, Daniel G. Reid (Downers Grove: InterVarsity,1993), has written one of the most helpful articulations of what this expression means.
I include an excerpt regarding terminology, and a concluding statement regarding the theological significance of the expression. I commend the whole article to you.
Here is an excerpt from the section on “1. Terminology”:
Numerous popular explanations of Paul’s doctrine of the Christian life argue, or assume, that the apostle distinguishes with these phrases between two parts or natures of a person. Following this misguided thinking is the debate as to whether the “old nature” is replaced by the “new nature” at conversion, or whether the “new nature” is added to the old (see Psychology).
The interpretation that ho palaios anthrōpos and ho kainos anthrōpos refer to parts, or natures, of a person is wrong and misleading. These terms rather designate the complete person viewed in relation to the corporate whole to which he or she belongs. Thus these terms are better translated as “old person” and “new person.” The translation “old self” and “new self” (NIV, NRSV) is too individualistic, since the idea certainly means the individual Christian (Rom 6:6), but is much more than merely individual. “Old person” and “new person” are not, then, ontological but relational in orientation. They speak not of a change in nature, but of a change in relationship.
The “old person” is not the sin* nature which is judged at the cross* and to which is added a “new person.” The “old person” is what believers were “in Adam” (in the old era). The “old” points to everything connected with the fall of humanity and with the subjection to the distress and death of a transitory life, separated from God (see Life and Death). Within the context of Paul’s theology, this concept carries with it deep undertones of God’s wrath* and the wages of sin. The “new person” is what believers are “in Christ” (in the new era). Paul directs us to the completely new, to the salvation* and healing that believers receive when they are crucified* with Christ and raised with him (cf. Rom 6:3-6; see Dying and Rising with Christ).
The conclusion, “4. Theological Significance,” addresses how life is now to be lived.
Life in the new age for the “new person” is to be lived out between the polarities of what has been redemptively accomplished by the historical achievement of the death of Christ and what is yet to be fully realized in the consummation of God’s redemptive program. Believers live in this temporal tension between the “already” and the “not yet,” and between the indicative (what they are) and the imperative (what they should become). Believers live in this “not yet” age, but their life pattern and standard of conduct are not to be those of this age, which are essentially human-centered and prideful, but of the age to come. Yet the struggle continues. While living as a “new person” in the new age, the basis for new life should be remembered. It is through the death and resurrection of Jesus Christ that the Spirit applies the benefits of the “new” life to the lives of believers. Life for the “new humanity” is living out, by the Spirit’s empowerment, what believers are because of Christ.