 As Neo-Daoism entered its last phase, another Daoist work, the Liezi, came to rival the “Three Great Works on the Profound.” Zhang Zhan (ca. 330–400) wrote an important commentary on the work—indeed, some would argue that Zhang had a hand in the formation of the Liezi itself—in which he recapitulated many of the ideas that spanned the entire spectrum of Neo-Daoist philosophy. What is of particular interest is that Zhang explicitly introduced Buddhist ideas into Xuanxue.