The correctness of any assertion within any of these systems can only be judged from within that system.
Your statement is plain false, Rick. In fact, it is often the case that an assertion within a certain system can only be judged from a position outside of the system. That insight is a consequence of Kurt Gödel's incompleteness theorem, which is proven to be true. And it is definitely relevant to the evaluation of the two systems Socionics and MBTT.