Nothing is more worth knowing than how our motivation and understanding work together as one mind. They do this in the same way goodness and truth work together. There is the same kind of marriage between motivation and understanding as there is between goodness and truth. We can get a clear idea of what this marriage is like from what I said before about goodness and truth.
Specifically, goodness is the essential reality of a thing, and truth is its visible existence. In the same way, our motivation is our life’s essential reality, and our understanding (which comes from our motivation) is our life’s visible existence. The good impulses in our motivation give themselves form in our understanding and make themselves visible.
When we do good things and have true ideas, we have motivation and understanding. But when we do harmful things and have false ideas, we do not have motivation and understanding. Instead of motivation we have desire, and instead of understanding we have knowledge.
A truly human motivation is a storehouse of good impulses, and a truly human understanding is a storehouse of true ideas. So we cannot call bad impulses “motivation,” or false ideas “understanding”—they are just the opposite, and opposites destroy each other. Because of this, when we do harmful things and have false ideas, we are not rational, wise, or understanding. Also, the deeper parts of a harmful person’s mind are closed, and our motivation and understanding are mainly in these parts of our mind.
We may think harmful people also have motivation and understanding, since they say they intend things and understand things. But their motivation is only desire, and their understanding is only knowledge.
from The Heavenly City, Chapter 2