So, granted that some things are beneath others, what things are beneath the human soul?
In a word: everything. In two words: every thing.
God created man in his image; in the divine image he created him; male and female he created them. God blessed them, saying: "Be fertile and multiply; fill the earth and subdue it. Have dominion over the fish of the sea, the birds of the air, and all the living things that move on the earth."
If "Man is the summit of the Creator's work," then everything else in creation (except angels, who technically aren't things anyway) must be beneath him. That would include, obviously, things man has created: sports and wine and poetry and countries.
Now, love is a kind of desire that reaches from the lover to the beloved. An act of love starts in the lover and ends up in what is loved. That's why what St. Thomas calls the "excellence" of an act of love is gauged by what is loved, rather than by who loves.
So if I love, say, my dog, the excellence of my love for my dog is measured by the excellence of my dog.
On the other hand, knowledge implies that something is added to the intellect. It starts in the thing known and ends up in the knower. The "excellence" of an act of knowing is gauged by what knows, rather than by what is known.
The excellence of my knowledge of my dog is measured by the excellence of me.
Despite what you may have heard, I am more excellent than my dog; I am, after all, the summit of the Creator's work. Therefore, my act of knowing my dog is more excellent than my act of loving my dog.
This doesn't mean that loving your dog is bad. But it does mean that loving your dog more than you love another person is bad, since love for any person is more excellent than love for any dog.
It also means that the purpose for learning about your dog cannot be to love your dog. More generally, the end of knowledge of other things in creation cannot be love of them. Why? Because the knowledge of other things is more excellent than the love of them, and the end of a thing cannot be less excellent than the thing itself.
What, then, is the end of knowledge of other things in creation? The love of God, of course, the excellence of which is gauged by the excellence of God Himself. Here, though, the important point is that it can't be anything less excellent than man.