principle

/ˈprɪn·sə·pəl/ n [C/U] (MORAL RULE)

Definition

› a moral rule or standard of good behavior or fair dealing: [C] His guiding principle is that everyone should have equal access to high-quality health care. [C] He refused to compromise his principles. on principle › If you believe or act on principle, you are following a personal standard of behavior: On principle, I never eat meat.

(Definition of principle n (MORAL RULE) from the Cambridge Academic Content Dictionary © Cambridge University Press)