Yang Xiong (YAHNG shee-ong), whose father was a petty landlord, read extensively in his early youth. Though he lacked eloquence because of a stammer, he had a free and natural air that enabled him to get along with people. He became skilled in poetry and was appointed the close attendant of the emperor.
Later in life, Yang Xiong turned to the study of philosophy and dialect. He set forth the concept of xuan, “dark energy,” or the absolute metaphysical reason for the formation and existence of all concrete things, in his Tai Xuan Jing (before 18 c.e.; The Classic of the Great Dark, 1983). He believed in the knowable nature of the universe and the importance of knowledge and stated that practicable knowledge was authentic knowledge. He also held that human nature was a mixture of good and evil. One became a good person by developing the good and an evil person by enhancing the evil.