Early on in my Christian life, I heard an illustration about how to grow. “Inside you,” the story goes, “live a white dog and a black dog. The white dog is truth, grace, love, beauty—everything good and positive. The black dog is hatred, selfishness, pride—everything evil and destructive. Every day, these dogs fight for dominance inside you. Whichever one you feed wins. So don’t feed the black dog!”
Later I learned this story isn’t actually of Christian origin; it supposedly has roots in a Native American tradition. Later still, as my theology became clearer, I realized it doesn’t even illustrate a Christian truth! The fundamental premise is wrong.
As the story goes, a Christian has two natures, constantly warring within—a fallen, sinful, old nature and a regenerate, holy, new nature. It’s a view you may have heard before; perhaps you still believe it even now. This notion is so common, it has actually made its way into a couple very popular English translations of the Bible. How confusing it is to read “sinful nature” over and over in Romans 7-8, Galatians 5, 2 Peter 2, and a few other places. Confusing and misleading, since the Greek word standing behind “sinful nature” is actually “flesh,” which has entirely different theological implications.
The “flesh,” as it’s used in these places, refers to a realm of life or a sphere of existence, not a personal nature living inside you. It’s part of the New Testament’s “Two Ages” perspective: this Present Evil Age vs. the glorious Age to Come. Multiple terms are used to contrast the two ages: Adam vs. Christ, law vs. grace, sin vs. righteousness, death vs. life, etc. Each of these pairs refers to a different aspect of the two competing realms: its founding father (Adam vs. Christ), its constitutional authority (law vs. grace), etc. One of the pairs, referring to the different operating powers in each realm, is flesh vs. Spirit.
Christians live now in a period between the times, where we are citizens of the New Realm but we still feel the pull of the Old. The point, when biblical writers refer to following “the flesh,” is that we still have the option to live under the influence of the Old Realm. It’s not that we are battling an evil nature still resident within. No! A Christian truly is a New Creation! But we are still tempted to give in to the power source of the Old Realm.
Gospel growth, then, is not changing who you are; rather, it’s becoming who you now are in Christ.