precept

[Cobuild] N-COUNT: A precept is a general rule that helps you to decide how you should behave in particular circumstances.[FORMAL]

• an electoral process based on the precept that all men are born equal.  
• =  principle   

[Am-Heritage] 1. A rule or principle prescribing a particular course of action or conduct.

[Thesaurus/WordNet 3.0]

1. rule of personal conduct.
   = principle
   
2. doctrine that is taught; "the teachings of religion"; "he believed all the Christian precepts"
   = commandment, teaching