The Carnal Christian?

First disappointing chapter of the Indwelling Life of Christ. Major Thomas is trying to get us to think about what kind of Christian we want to be. This is a good thing to think about but the way he argues for a carnal Christian is weak.
First, we must ask if there are truly any Carnal Christians or do we just have carnal/fleshly moments. This would take us back another step. This would be to think about what it means to be born again. Truly many people claim to be born again believers but their lives reflect nothing of the Savior who demands allegience and died for them.
John Piper wrote an excellent book on what happens when one is born again and the results of that new birth. I think a very short synopsis would be to say that to be born again is to have God himself give us a new heart, give life to a lifeless spirit, enabling us to see and value Christ as our highest treasure and greatest good. I do not believe that the concept of a Carnal Christian can fit inside of being born again.
Second, I think that his use of 1 Corinthians 3:15 is completely out of place. This reference should not be used to argue for the existence of carnal christians. The context that this verse is found in is a passage about church division, not about carnal lives. Can they be related, yes, but not directly in this verse. What we must realize with this verse is that as Paul goes on in the letter we see pretty clearly that not all those in the church were genuine believers.
I agree with the author that we need to think about how we are living out our Christian life. However, I do not think that we can choose what kind of Christian we want to be. There is only one kind of Christian. That Christian is born again and at the root of their being, because of the regenerating work of the Holy Spirit, they desire to live lives surrendered to the Lordship of Christ even if they still struggle with the flesh. If we allow people to believe that there is a choice then we are doing great damage to the church and are not being faithful stewards of God's Word, which calls people to repentance.