I think it's funny how people say that MBTI has no evidence of existing, and yet here we all are. We are all obviously different; and one of the 16 personality types generally fits everyone. The evidence is in the people... the people of the world. That's the evidence. How else do you study social science? One could just simply write off all social science on the same grounds of MBTI. It's observed through a different lens that MBTI is observed in, but you use the same eyes to identify social science principals and MBTI principals (with a different lens for MBTI).