The Principle Approach (PA) is not the most well known approach out there and I always struggle with coming up with a concise definition. So I'm just going to provide a few links for anyone who is curious:
Principle Approach is a life-long study because it deals with applying biblical principles to every subject and hence to all of life. The method is researching and reasoning. The purpose is inspiring a love for God. The goal is liberty through self-government.