A possibility and limitation on Mengzi (孟子)'s Seizensetu (性善説 = the ethical doctrine that human nature is essentially good)
Mengzi (孟子) thought that there is no essential difference between Junzi (君子) and Xiaoren (小人). And he advanced human nature is essentially good as a ethical existence. By this view all humans have a possibility to become a Shengren (聖人). As a result, human nature became all equal before Seizensetu (性善説). But, it also means Mengzi limits the human nature's other possibilities.
And Mengzi advanced three methods of learning, Qiu Fangxin (求放心), Gua Yu (寡欲), Yang Qi (養気). But Mengzi never explained these methods concretely. It means that Mengzi's Thought lacks a thought of concrete method. This is a structural limitation on Mengzi's Thought.