But diligent studies in the evening eventually enabled him to gain an honorary Ph.D. from Yale University and become a college professor.
靠著不斷的苦讀自修，他在史哲文等方面都有高深的造詣，尤其精治先秦兩漢史。雖然沒有正式文憑，卻被聘為大學教授，而且曾獲香港大學及美國耶魯大學榮譽博士學位。