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.
Our brains work like computers: They input data and process it in accordance with their wiring and programming. Any opinion you have is made up of these two things: the data and your processing or reasoning. When someone says, "I believe X," ask them: What data are you looking at? What reasoning are you using to draw your conclusion?
Dealing with raw opinions will get you and everyone else confused; understanding where they come from will help you get to the truth.