principle noun definition in Moral topic from the Oxford Advanced Learner's Dictionary

principle

 noun: Moral topic
[countable, usually plural, uncountable] a moral rule or a strong belief that influences your actions He has high moral principles. I refuse to lie about it; it's against my principles. Stick to your principles and tell him you won't do it. She refuses to allow her family to help her as a matter of principle. He doesn't invest in the arms industry on principle.