  By the thirteenth century, students of the Daodejing were already blessed, as it were, with an embarrassment of riches, so much so that Du Daojian (1237–1318) could not but observe that the coming of the Dao to the world takes on a different form each time. That is to say, different commentators were shaped by the spirit of their age in their approach to the classic, so that it would be appropriate to speak of a “Han Laozi,” “Tang Laozi,” or “Song Laozi,” each with its own agenda (Xuanjing yuanzhi fahui, Daozang no. 703).