For Zhu Xi's explanation of the phrase “ge wu,” see his commentary on Great Learning... For Wang's interpretation, see his “Questions on the Great Learning”... Unfortunately, the key word “ge” is highly ambiguous, so both interpretations ... are completely defensible... Nivison... described the phrase as “a philologist's delight,” because of the endless speculation it could provoke, and argued that “[n]o one will ever know what it really meant in its locus classicus.”