Principles are ways of successfully dealing with reality to get what you want out of life.
Ray Dalio, one of the world’s most successful investors and entrepreneurs, cites principles as his key to success.
Proximate causes are typically the actions (or lack of actions) that lead to problems, so they are described with verbs (I missed the train because I didn't check the train schedule). Root causes run much deeper and they are typically described with adjectives (I didn't check the train schedule because I am forgetful). You can only truly solve your problems by removing their root causes, and to do that, you must distinguish the symptoms from the disease.