When Paul talks about flesh and Spirit, he's not talking about two different kinds of behavior. These aren't two different ways to act. He's talking about two totally different kinds of life. Two different men, two contrary natures. Walking in the one means leaving the other behind. The two are contrary to each other and they pull against each other. The flesh lusts against the spirit and the spirit against the flesh.
Sometimes people read passages like this and don't see the enormous divide between these two things, flesh and spirit. In other words, Christians sometimes think that walking in the Spirit has to do with simply following where the Spirit is pointing, or taking instructions from God, but no, it's not like that. Walking in the Spirit isn't taking our instructions from the Lord. It's finding our Life, our reality, our country and kindred and father's house in the Lord, as the Lord. It's seeing as He sees, walking where He is, living in the Light of what He has done.
Think about this for a minute - what is walking in the flesh? Is it just a matter of checking in with the flesh during a 15 minute morning quiet time? For us to walk in the flesh, does that require some daily discipline where we try to get a feel for what the flesh wants today? No, that's silly. We all know it's a much bigger and deeper reality than that. Walking in the flesh has to do with living in and by a nature that defines what is real to you. How do we walk in the flesh? It's perfectly natural and effortless when we are seeing with fleshly eyes, desiring fleshly things, understanding with a carnal mind, and relating to our environment with five natural senses. Walking in the flesh has to do with where you think you are, what you think you are, and what you think is good, true, real, and right. It's a deep and comprehensive worldview. It is a nature and reality that permeates every pore of your being.
Therefore, what is walking in the Spirit? Walking in the Spirit is exactly the same thing with the exact opposite nature and order. Walking in the Spirit has to do with living in and by ANOTHER nature that defines what is real to you. Walking in the Spirit involves seeing with the Spirit's eyes, discerning eternal and spiritual reality, and understanding with the mind of the Lord. Faith accesses the grace in which we stand. When we walk by faith, or walk in the Spirit, we are simply talking about living where we know ourself to be, living according to what we know we are, and what we think is good and true and real and right. It, too, is a nature that permeates every pore of our being and defines the nature and order of our existence.
Neither one of these take effort. Neither walking in the flesh or walking in the Spirit are a matter of effort. They are both a matter of awareness, light, consciousness.
You will live the life that you are seeing. You will walk in the realm that is real to you. And consequently, you will be free from what you are not seeing, and what has ceased to be real to you. That is the heart of sanctification.
This is why Paul says in Galatians, "Walk in the Spirit and you shall not fulfill the lust of the flesh." He doesn't say, "Walk in the Spirit, and for heaven's sake, try harder not to fulfill the lust of the flesh." Can you see the difference? The awareness of the one becomes the end of the other. The consciousness and experience of the one becomes the separation from the other. When the Spirit becomes what you see and what is real to you, the desires of the flesh are crowded out. They lose their power and relevance and pull because you feel very unrelated to that realm and that man. Like Christ, who left that world and divided Himself from it, you too start to feel sanctified, set apart, by a living faith.
That is why he says in verse 18 that the one led by the Spirit is not under the law. The one who is walking in the Spirit does not need a law to tell him how to behave in the flesh. The one who walks in the Spirit is crucified to the flesh, dead to it, unrelated to the man who needed law and yet always disobeyed the law. If we walk in the Spirit we are free from the law because the nature and order of Christ becomes the Life that operates in us.
Walking in the Spirit isn't something that we strive to do any more than bearing fruit is something that we strive to do. Both of these, Paul says, are the byproduct of sanctification - knowing and experiencing the divide of the cross. These things are the natural result of seeing where we are and forgetting where we were, or becoming aware of one Life and not looking back upon the other.
Again, there is the fact of what God has accomplished. In Galatians 5 Paul says it like this, "Those who are Christ's have crucified the flesh with its passions and desires." That's the fact of the great divide.
