The philosophy of Agatha Christie

This is Amy Leatheran in Murder in Mesopotamia, channeling Schopenhauer:

Somehow, the more I get older, and the more I see of people and sadness and illness and everything, the sorrier I get for everyone. Sometimes, I declare, I don't know what's becoming of the good, strict principles my aunt brought me up with. A very religious woman she was, and most particular. There wasn't one of our neighbours whose faults she didn't know backwards and forwards...