"A pure human soul that is undivided and static does not, and perhaps cannot, exist.
Without anything to struggle against, without any resistance, there is no progress.
As the Chasidim used to say, “If God wanted man to be like that, He would have done better to create a few million more angels.”
The angels are limited.
They are static and each is eternally the same.
The human soul needs to be challenged by the animal soul for the sake of the individual’s growth, and it is not fair to call the animal soul evil because it merely does its duty.
Its duty is to tempt; its deepest hope is that the person is not tempted.
In a famous story in the Zohar, the king hired a courtesan to lure his son into evil ways, wishing she might fail.
The dilemma of the courtesan, the animal soul, is obvious."
From Pebbles of Wisdom from Rabbi Adin Steinsaltz (forthcoming)