The intellect (mind) is capable of all kinds of self-servin…

The intellect (mind) is capable of all kinds of self-serving evil and deception.
How can that be part of the soul?
I think the body/soul dichotomy you are using is a very low resolution analysis that leads to more problems than it solves.
Personally, I make a very strong distinction between soul and mind. The soul is the seat of ethics and morality (knowledge of what is good). The mind can be used for good by the soul, if the soul is in charge, but if it isn't the mind is an extremely cunning deceiver and adversary.
I'd even go as far as to say that Christ, Lucifer and Satan are represented inside of us:
The soul, like Christ, is the connection to the Father, the mind, like Lucifer, is a deceptive talking snake, and the body, like Satan, is just an animal, a beast.
I'm happy to hear your objections, I'm writing a book about it and prefer to be aware of the arguments of those who disagree with me.