He has his own, presumably unsatisfactory, definition and goes on for another 100 pages commenting on it. Now it is quite possible that the qualities we need for success in this life cannot be put into words. But to exhort us to love one another under penalty of failing as a person or society makes no sense. We are asked to exhibit an undefinable emotion which is, in any case, a gift. Love is a feeling we can neither gain nor merit.
Respect requires a decision and an action.
I can extend and fulfill my obligations without ever having those feelings that tell me I'm in love. The difficulty in loving can be universal. He then goes on about all he does for his son and tells why. Cause you are my son. You my flesh and blood.