Mencius
So a jūn zǐ is somebody who has managed to hold onto the gifts that Heaven has given him, the gifts that can make humans act with benevolence, be led by a sense of duty, want to act in ways that will keep good relations with others, and try to aid and protect people who are being treated unfairly. To be a real jūn zǐ, the person has to have these true feelings and to act on them. It is not enough just to act as though one has these feelings.