Quite the contrary, the Lord makes specific mention of the root. If you look in 7.15 it speaks of the outward and the inward. The inward man, that is the man of the spirit, is either good or bad and therefore, the whole tree is either good or bad. That is what Jesus is speaking of in the context of 12. The view of the teachers of the Law was that they could clean the inside by the outside, but flesh does not give birth to spirit. The obvious is that they were judging by the outward and by the works of the law were proclaiming the inside clean, so that they make themselves as God, their own savior. In 7 the context is the rebuke of judging by the outward, they are therefore to remove the log (of the law that blinds them to their own sin) out of their eye. Thus 7.15 is the same as the warning to beware of the levening of the workers of the Pharisees. The context is clear, it is the doctrine of TRUTH, not deeds. Look back to Chapter 6 about swearing oaths and remember the oath of the Israelites and how the "cleansing of the outside," could not make them clean on the inside, instead it brings forth death and the curse. And, remember that the giving of the law did not open their eyes, in fact even to today, when Moses is read the veil is pulled over their eyes.

You have injected your thoughts and made the two trees of 7 and twelve to be the same in all way. The root is the source of goodness, not the tree. In the one they look at the fruit of the outside, Jesus not keeping their law, therefore fruit is bad, the tree must be bad. In the other, they see the fruit which is good, i.e. the works that he is doing, and say that the root is bad, i.e. the tree is bad. Jesus is fed up, either make one good or one bad. It is the Root of David who is also the Firstfruit, and if the root is good so also, the fruit, so quit judging by the outward appearances.

Matthew 12, completely refutes your assertion that there are not two distinct natures in us. James speaks the same wisdom, for though it should not be that sweet and bitter should come forth from the same well, it is the case.

I think that you do not comprehend the Reformers correctly. Paul most assuredly taught a new nature, the NEW MAN, not concieved as the first Adam, nor has God infused righteous into us. But, as Paul said all that matters, is the new nature, the New Creation. This is that which is supported by the root. The abiding is not in our flesh, it is by the root that the tree is supported, Christ in the new nature, created in the likeness of Gods own dear son, not in the likeness of the flesh, always and only produce good fruit. Paul was not just making his old nature new and improved only in need of tweeking. It is destined for destruction, not restoration. Except that the old be removed, the new shall not come.

Weslyan Perfectionism speaks exactly according to the doctrine of self-sanctification, that is the cleaning of the inside by the outside. When Wesley rejected the teaching of the Reformers he again embraced the legalism of dead works according to the Arminians. The mixing of flesh and spirit was a of primary concern to Calvin in his discourse against the heresy of Osiander. And though of a different type, the gnosticism of essential righteous is still the same Pelagian error, that we have an native righteousness that is capable of producing good works. The errors of the Scholastic and Papists are really no different.

Either the tree is wholly good or it is fit only to be cast into the fire. Which is what Jesus said. We do not live by sight, but by faith in the Son of God, in whom we are hidden, and in him there is not sin. Matthew 12 is a repudiation of this mixing of wines, light and darkness, good and evil. Either the New Man within is created in perfection though not yet mature, and obviously not yet manifested, or, it is possessed of evil. A blasphemy, if I am not mistaken is exactly, what Jesus is talking of. Again, though, Jesus makes appeal to the idleness of words, so that doctrine, true and false is in sight it is not the main point. Out of their hearts they were speaking blasphemies because they did not recognize the Son in their midst. So, on the one hand the context of the two tree teach is immediately the false hope of the Law, of a man who is just like God, in the other is the false hope of a Christ who is just like man. But Jesus came both God and man. Jesus was exposing their hypocracy as it was obvious that they were speaking two different doctrines.
And, neither were correct.

Do not take this to mean that we are gods because he has called us his sons. But, neither has he mixed the two natures. He is immediate with us in our New Man, he is not, nor could he ever be one with the evil one, that is the old nature. But a man does not put new wine in old wine skins, period. Matthew is unequivocal about this issue, namely that only out of his good treasure does a man bring forth good things. We speak both good and evil, but the one cannot have the same well spring as the other. A house divided against itself cannot stand, but we have the owner of the house who is both its builder and owner, and its occupant, it is not divided. But, in this person, who we are these two nature, never mingled war incessantly.

Again it is Weslyan, or at least pietistic legalism, not sanctification through the Spirit that you propose, no I. I have just re-read Calvin, and he does not make the two natures one, flesh and spirit, co-mingled, nor would you ever find this revelation in Scripture. Spirit gives birth to spirit and flesh to flesh. We are, however in this body, both natures, good and evil in one person. But, just as the two natures of Christ are not confused, neither are ours.

Paul make the absolute separtion also in Romans 7. If there is a one to one correspondance with the person and what he does, you're damned, unless you are confessing perfection. Paul makes his place of worship, not the external but his mind. And, he testifies in another, that we have the mind of Christ, not the mind of the old nature, not a mind of evil. The same absolute separtation is made in Galations. It is an error to say that we are to work along with the "influences" of the spirit. This is the heresy of infused grace. The would that you "may" not do as you want, is directed to the desire of our new heart, created in the image of the Son, who always does the will of his Father. It is true that the Spirit wars, but we are the vessel of his wrath against all wickedness and deceitful practices of man by which he suppresses the knowledge of God. The mystery that you are talking about is why God does not prevent our sin at all time. To that I would direct to Hebrews 12. Surely you do not believe that the Spirit can lose the battle, do you? And, do think that we can lose? "For in this world you will have tribulation, but...Peter, Satan has desired to sift you...but I have prayed for you." We never lose, it is impossible that we should not perservere.

You have rightly said that we will sin. And, we have to bear the responsiblity for the action of the old nature. But, is not that also what Christ came to do, and not to redeam the old nature but to destroy it. So it is written that in Christ sin, the flesh, which is the old nature, has been circumcised from us, no long shall it have any part in us. We do not merely walk by the influenc of the Spirit. But, the works of the two distinct natures are evident. So, we walk by faith, not by sight and we walk no longer after the ways of the flesh, but by the Spirit.

I would encourage you to quit reading the Scripture according to your traditions. 1 John tells us that we do not go on practicing sin because his seed remains in us. Indeed, it is impossible that we, (our new man) can go on sinning, for in him there is no sin. John is in perfect concert with Paul. It is no longer I who sin. But, if we do sin.... The apparent contradiction is explained by John's gospel Chps 14 through 17. Perhaps you are one of those who believe that you can walk in and out of the Spirit. These chapters rule out any such doctrine. Now, if you are thinking that this is soley referring to the parousia, or that the epistles are merely talking about our "walk" let me disabuse you of that, by directing your attention to 14, especially verses 16 through 18, and then again in 17.20-26. This singular discourse is not without its relevence. If you are in him you are in him, and if you are in him then he is in you, and neither is without the other, for his seed remains in you, but if you do not have the Spirit you are none of his. You can neither love him nor remain in him unless you are of him, that is his seed. Unless of course you thing that you can divide out of your body your mother from your father. But if he is in you then the love of God has been shed abroad in your heart and it always follows the will of the Father.