Thus love is the most easy and agreeable, and gratitude the most humiliating, affection of the mind. We never reflect on the man we love without exulting in our choice, while he who has bound us to him by benefits alone rises to our ideas as a person to whom we have in some measure forfeited our freedom.

The Citizen of the World, Or, Letters from a Chinese Philosopher Residing in London, to His Friends in the East (ed. 1800)