I read an article a while back in which the author assumed that Liu Xiaogan's 1994 Classifying the Zhuangzi Chapters had established that the Zhuangzi “inner” chapters were by a single author and of an earlier date than the rest of the Zhuangzi. Clearly the author had not seen my 1997 review in Asian Philosophy, which shows that Liu’s arguments in fact do not support these conclusions. To make the review more easily available, I’ve posted it below, with the original pagination indicated in the pdf.
Let me add that I myself agree that some parts of the Zhuangzi “inner” chapters—though certainly not all—express a roughly consistent point of view and could be by a single author. I also think that some parts of the “inner” chapters are likely to be earlier than parts of the other chapters. On the basis of literary style, for instance, I think the opening dialogue of “Autumn Waters” is probably of a later date than, say, the opening passage of “Xiaoyao You” (the first of the “inner” chapters). (On the other hand, I also suspect that Chapter 6, “The Great Ancestral Teacher,” includes Qin or Han dynasty material.) But I have yet to see a convincing argument for the privileged authorial status and early date of the “inner” chapters as a whole. In my view, neither Liu’s work nor Graham’s “How Much of Chuang tzu Did Chuang tzu Write?” makes the case successfully.
Postscript: Were I to rewrite my review of Liu’s book today, I would emphasize more strongly the incoherence of its treatment of the “inner” chapters. The book acknowledges that some portions of these texts—such as the stories about Zhuangzi and Huizi in chapters 1 and 5—may be of a significantly later date than others. In doing so, it accepts the possibility that the texts could contain material by different writers, added at different times. Yet the book’s main arguments concerning authorship and chronology are inconsistent with this stance, as they turn on treating the “inner” chapters as a homogeneous whole.
I’ve posted some further reflections on the authorship and chronology of the Zhuangzi in this blog thread.
Update (2012): On textual problems in Zhuangzi, see now the recent work of Esther Klein and David McCraw.