<Snipped quote by Host>
-Soren- *opens his mouth, and then closes it, thinking* Why does he attach importance to those things? Is it only for some benefit of his own--as in, she is useful to him--or does he care in order that he might benefit her without necessarily benefiting himself?
Does anybody truly do anything unselfishly? Even if the answer to that is yes, Serenity is very advantageous to Luke, so I cannot fairly answer the second question, since her simply being alive is advantageous to him.