The Two Natures in the Child of God by E W Bullinger and published by Classics.
The experience of the child of God is described, in Galatians 5:17, the following words: "the flesh lusteth against the spirit, and the spirit against the flesh: and these are contrary the one to the other; so that ye cannot do the things that ye would."
In everything but this the mere professor can imitate the true child of God: and it is this which distinguishes the merely religious person from the real Christian. Every true child of God always has an abiding experience of conflict within, as described in Galatians 5:17. But not every child of God understands the doctrine concerning it. To have the experience without knowing the doctrine is the fruitful source of confusion, disquietude, and discouragement. To know the doctrine and not to have the experience is fatal, and means eternal disaster.
The only remedy for this is to learn, direct from the Word of God, all that is there taught concerning the nature inherited through generation by Adam, and the nature bestowed through re-generation by God.
When the doctrine of the two natures is clearly understood, then, that which before was the cause of doubt is not only removed, but it becomes the ground of assurance; and is, indeed, the best assurance that one can ever have that he is God's workmanship, and that God has actually begun in him that good work which He Himself will perfect and complete (Philippians. 1:6).