moral compass

Short definition from Wiktionary

Noun

1. 1
   An inner sense which distinguishes what is right from what is wrong, functioning as a guide for morally appropriate behaviour.
2. 2
   A belief system, person, etc. serving as a guide for morally appropriate behaviour.
3. 3
   The full range of actions, vices, or virtues, which may affect others and which are available as choices to a person, group, or people in general.