The reason why a battle develops at this point [in the process of regeneration] is that our inner self has been reformed through truths. These truths allow us to see what evil and falsity are; but we still have evil and falsity in our outer or earthly self. At first, therefore, a disagreement arises between our new will, which is above, and our old will, which is below. Because these two wills are in disagreement, what they delight in is incompatible as well.
As we know, the flesh is against the spirit and the spirit against the flesh; the flesh and its lusts have to be brought under control before the spirit can become active and we can be a new person [Romans 7:22–23; Galatians 5:16–17, 24–25; Ephesians 4:22–24; 1 Peter 2:11].
After this disagreement of wills occurs, a battle develops, which is what is known as a crisis of the spirit. This inner conflict, this battle, is not between good and evil [directly], but between truths that defend what is good and falsities that defend what is evil. Goodness cannot do its own fighting; it fights through truths. Evil, too, cannot do its own fighting; it fights through falsities. Likewise, the will is unable to do its own fighting; it fights through its understanding, where its truths are kept.
That battle is something we feel inside ourselves and nowhere else; we experience it as an attack of conscience. In reality, though, it is the Lord and the Devil (meaning hell) that are fighting inside us. They fight for control over us, or to see whose we will be. The Devil, or hell, attacks us and summons the evils that are inside us. The Lord protects us and summons the good things that are inside us.
Although this battle takes place in the spiritual world, it is also a battle inside ourselves between the truths that defend what is good and the falsities that defend what is evil within us. Therefore we have to join the fight as if we were acting completely on our own. We have free choice to act either on the Lord’s behalf or on the Devil’s behalf. We are on the Lord’s side if we stay with the truths that defend what is good. We are on the Devil’s side if we stay with the falsities that defend what is evil.
It follows from this that whichever self wins, whether it is our inner self or our outer self, it will control the other. It is entirely the same as two enemy monarchs who fight over which of them is going to rule the other’s country; the one who wins gains control of the other’s territory, and all who live there have to obey their new ruler.
In this case, if our inner self wins it rules and gains control of all the evils in our outer self; our regeneration then continues. If on the other hand our outer self wins, it rules and drives away all the good qualities in our inner self; our regeneration then ceases.
from Regeneration, Pages 66-68