Born during the T'ang dynasty (618-907 A.D.), Su Wei-tao was able to write essays by the tender age of nine. When he was just 20 he successfully passed the imperial examinations and took a personnel post in the civil service. After assuming the throne, the empress Wu Tset'ien (625-705; the first woman to rule as emperor) appointed him as her prime minister. In order to protect his position, Su ingratiated himself with everyone, while in dealing with affairs never expressed a clear-cut opinion or idea. He was therefore never renowned for administrative achievements. If he were to take a definite stand, he would have to bear responsibility for his actions.
This ambiguous behaviour is described by the Chinese as "Mo Leng". Mo means to grope or feel, while Leng is a corner or angle of an object. This suggests someone who grasps both sides or takes no definitive stand on any matter.
Later generations then used this expression to describe those persons with such equivocal natures.
(Gerald Hatherly)