nonempty set

syllogistic logic developed by Aristotle has a substantial presumption ,that is,a categorical proposition has a existential import,its subject has to refer to a non-empty class.

传统词项逻辑预设直言命题主项非空,尽管可以使包括单称命题在内的对当关系全面成立,但是又带来词项逻辑不再具有普适性等诸多问题。