It is not at all certain that there ever was such a personage as Käng-sang Khû, who gives its name to the Book. In his brief memoir of Kwang-dze, Sze-mâ Khien spells, as we should say, the first character of the surname differently, and for the Käng ( ), employs Khang ( ), adding his own opinion, that there was nothing in reality corresponding to the account given of the characters in this and some other Books. They would be therefore the inventions of Kwang-dze, devised by him to serve his purpose in setting forth the teaching of Lâo-dze. It may have been so, but the value of the Book would hardly be thereby affected.
Lû Shû-kih gives the following very brief account of the contents. Borrowing the language of Mencius concerning Yen Hui and two other disciples of Confucius as compared with the sage, he says, 'Käng-sang Khû had all the members of Lâo-dze, but in small proportions. To outward appearance he was above such as abjure sagehood and put knowledge away, but still he was unable to transform Nan-yung Khû, whom therefore he sent to Lâo-dze; and he announced to him the doctrine of the Tâo that everything was done by doing nothing.'
The reader will see that this is a very incomplete summary of the contents of the Book. We find in it the Tâoistic ideal of the 'Perfect Man,' and the discipline both of body and mind through the depths of the system by means of which it is possible for a disciple to become such.