The poem “Nam quốc sơn hà” is extremely famous, especially it’s first two lines:

“The Southern Kingdom’s mountains and rivers are occupied by the Southern Emperor,

This is clearly demarcated in the thiên thư.”

What exactly was this “thiên thư”? This expression has been translated into English by such terms as “Heaven’s book” and the “celestial book,” but what exactly was this “book”?

There is no way to know for sure. Some Vietnamese scholars have guessed that it might have been a text revealed through spirit writing. That is a reasonable guess, but there is no way of proving this.

While this poem dates from late in the eleventh century, in 1008 a “thiên thư” was discovered at the Song Dynasty capital. To quote Suzanne Cahill who wrote about this incident,

“On February 12, 1008, a gate keeper of the imperial city found a yellow silk scroll, sealed and bound up with a blue cord, hanging from a roof tile at one of the gateways of the imperial palace. The Song emperor Zhenzong (r. 988-1022), declaring the scroll an auspicious gift from heaven, named it the “Heavenly Text” (天書 [i.e., thiên thư]) and received it with great fanfare.”

The story about this text and its discovery is complex, but Cahill notes that Chinese historians have interpreted it as a “reaction to the perceived military might of the Khitan or as a result of the political factionalism then dividing the court or both.” In other words, the appearance of this text provided divine backing for the emperor and his policies during a time of danger.

[See Suzanne E. Cahill, “Taoism at the Sung Court: The Heavenly Text Affair of 1008,” Bulletin of Sung-Yuan Studies 16 (1981): 23-44. The quotes above are from page 23.]

The thiên thư mention in the poem, “Nam quốc sơn hà,” appears to have played a similar role as the thiên thư which was discovered at the gate to Song Zhenzong’s palace. Nonetheless, we have no way of knowing for sure what exactly it was.

In later centuries, Vietnamese scholars used the term thiên thư in ways which are more easily understandable. It appears that what was probably originally some kind of text which was produced in a Daoist setting, eventually came to be “Confucianized.”

Confucian scholars believed that there were patterns (văn) in the heavens and on the earth. These patterns were then brought into concordance through the writings (văn) of Confucian scholars. It was through the moral uprightness of Confucian scholars that kingdoms and all of their rituals and rules were established and recorded. As this happened, the borders of these kingdoms became linked to the celestial patterns in the sky, creating a concordance between Heaven, earth and man.

In the early nineteenth century, we can find the Nguyễn Dynasty scholar-official, Lê Quang Định, using the term thiên thư in reference to this process. The following quote comes from a document which he wrote to notify the emperor, Gia Long, about the completion of a new geography of the realm. Part of that document went roughly as follows:

“For the more than 1,000 years from the time of King Kinh Dương and Lord Lạc Long up to the Lý, Trần and Lê, the thiện thư terminated at Hoành Sơn. Our arrayed worthies [i.e., the Nguyễn ancestors] established a domain which covered the area of Champa, Chân Lạp and the four subprefectures of Qui Nhơn, Hoài An, Quảng Nam and Bình Thuận. [At that time,] the land was still divided at the Linh [a.k.a. Sông] River. The people did not understand writing, and governmental institutions were numerous and disorderly. August Heaven graced us with its assistance in establishing a court. Starting from the east, it came to encompass the southern periphery. The borders were brought in order and the land was united as one. The transformative teachings [i.e., “Confucian” teachings] penetrated everywhere.”

[Trần Văn Giáp, Tìm hiểu kho sách Hán Nôm, Tập I (Hà Nội: Thư Viện Quốc Gia, 1970), 331.]

What Lê Quang Định was talking about here is this process by which the patterns of heaven and earth come into concordance through the actions of morally upright individuals. The Nguyễn ancestors had been such people, and through their actions, the “transformative teachings” (聲教, thanh giáo) were able to spread to areas south of Hoành Sơn. The result of such actions was that the thiên thư then extended to areas south of Hoành Sơn as well in order to bring the patterns in the heavens into alignment with the changes which had taken place on earth as a result of the actions of the morally upright Nguyễn ancestors.

I think a good way to translate thiên thư in this context is as “celestial scripting.” I have never found this term used like this in any Chinese sources. I think that in later centuries Vietnamese Confucian scholars looked back at earlier historical records and saw this term in the “Nam quốc sơn hà” and then reinterpreted it in order to get it to fit their view of the universe.

So while it is not clear what thiên thư actually refers to in the poem, “Nam quốc sơn hà,” the meaning of this later usage as “celestial scripting” is quite obvious.