I have now reviewed the context of Han astronomy so far as it relates to the Zhou bi, and tried to show how the contents and origin of the book can be understood within that context. From the Han dynasty onwards the nature of our discussion changes, for the Zhou bi is no longer the property of an active group of astronomical thinkers, but becomes a classical text subject to the labours of commentators and editors.

So far it has been necessary to be cautious in speaking of ‘the Zhou bi’, for we have had no guarantee that the term referred to anything that had yet taken on a fixed form and content. If my tentative explanation of the process by which the canon was closed is correct, the Zhou bi waited at least two centuries before Zhao Shuang saw it, and in that interval it certainly seems that the text suffered some damage and corruption. But a careful reading of the present text and its three commentaries suggests that since the time of Zhao the text has not changed apart from a few minor copyist's errors. The object of this section is to tell the story of how the Zhou bi came down to the present day. In the process it will be interesting to say something about its later influence, without becoming too involved in the historical complexities of pre-modern Chinese debates on astronomy and cosmography.

The Zhou bi in the period of division

From the break-up of the Han in AD 220 to the reunification under the Sui in AD 581, China underwent three centuries of division and political chaos.