"Augustine says that all emotions are caused by love. Therefore hatred also, since it is an emotion of the soul, is caused by love... Nothing is hated, save through being contrary to a suitable thing which is loved. And hence it is that every hatred is caused by love." (pg 445)When I read this statement, I about fell out of my chair. (I have fallen out of my chair from reading such good stuff written by Thomas.) I had never thought of this before, that the existence of hatred stems from love. It made me think a possible reason Satan fell from his status of an angel of God. He began to love himself. Once Satan began to love himself, consequentially he began to hate God. So the first hater became a hater because he was a lover.
Thomas defined love as Aristotle did (no surprise there.), "to love is to wish good to someone." I won't dwell on this definition. One point of clarification, Thomas intended "someone" to be able to mean oneself or anyone else.
The essence of Thomas' point is that love is a cause of hate. When we hate something or someone it naturally follows "what are we then loving?" For instance, I hate it when people talk or make unnecessary noises in the library. What causes this hate is my love for a quiet place where I can work in peace.
In application, one can see how this can help us discover what we really love. When you find yourself hating something or someone, it is good to begin exploring back to find what it is that is causing this hate, what exactly are you loving that is contrary to this hated object. By looking at what we hate, we're able to search back to find out what fuels our passion which love "preserves and perfects." (pg 443)