We have two abilities that make up our life, one called will and the other understanding. They are distinguishable, but they are created to be one. When they are one, they are called mind; so they are the human mind, and it is there the entirety of our life is truly to be found.
Just as all things in universe (those that agree with the divine design)trace their origin back to goodness and truth, so everything in us traces its origin back to our will and understanding. This is because whatever good we have depends on our will and whatever truth we have depends on our understanding. These two faculties, these twin living parts of us, receive and are acted upon by what is good and true: our will receives and is acted upon by everything that is good, and our understanding receives and is acted upon by everything that is true.
Goodness and truth can be found nowhere else in us but in these faculties.
from Regeneration, Spiritual Growth and How It Works