Quote Originally Posted by Schildmaid View Post
Well, it makes more sense when it's about values, so I'll just go make up my own theory if it's not about values. I mean, I thought the whole basis of calling types rational or irrational was that the rational ones had leading functions that involved making judgments, thinking being about epistemic judgments and feeling about situational judgments (see here: http://wals.info/chapter/76), which are also called facts and values. If it's literally just about thinking or feeling we may as well go do MBTI and talk about how cold and unfeeling we all are since we're INTJ Masterminds. I could have sworn I've seen some authors make it about facts/values even if not all do though.
Honestly -- the rational/irrational dichotomy is itself rather obscure. I see it as being more closely related to symbolic thinking vs experiential, picture-based thinking, rather than judgments vs perceptions. But in any case, it's not one of the stronger categories in socionics, compared to logic, ethics etc. Don't abandon socionics just because of that

As for epistemic and situational judgments -- they seem similar from an IM point of view. Roughly speaking, "may" = Ne, "must" = Se (with Ti).