When one encounters so many broken promises - from family, from friends, from subjects - you... begin to just wonder if there's such a thing as a promise that can be kept. My family once had a stance much like yours, but after Father's death, everything we'd ever stood for just flew out the window, so to speak.
To be able to make a promise to Boq that I could keep would redeem me, so to speak - All of Oz views me as wicked, and if I could just show them that I have at least a shred of compassion within this heart, things might be just a little brighter for me.