What inspired me is that the daughter – Isabel Briggs Myers of the mother daughter team (mother, Katherine Briggs) who created MBTI, was INFP – and her mother was INFJ.
I thought: If an INFP/INFJ _CREATED_ the 16 temperament breakdown then surely I as an INFP could also figure out all 16 as well. And I could. I figured their way-of-thinking was somewhat embedded in the test itself – and I think it is.