TL;DR: Không vong, also called tuần không or tuần trung không vong, is the two earthly branches that do not appear within a ten-day cycle of the can chi (heavenly stem and earthly branch) sequence. For example, in the Giáp Tý cycle, Không vong falls on Tuất and Hợi. The lookup is short: determine which of the six Giáp cycles the day pillar belongs to, then compare that cycle's missing branch pair with the branches in the four pillars. The old books read Không vong together with other methods: Tam Mệnh Thông Hội weighs it by the life stages and the stars that accompany it, while Tăng San Bốc Dịch, a Lục Hào book, holds that prosperous or moving lines are not counted as void.
What Is Không Vong in Bát Tự?
Không vong is the two earthly branches missing from a ten-day cycle of the can chi sequence. The can chi cycle pairs ten heavenly stems with twelve earthly branches, so after every ten days two branches remain unpaired, and those two branches are called Không vong, also written as tuần không or tuần trung không vong, in Chinese characters 空亡 and 旬空. In Bát Tự, Không vong is not inherently a good or bad star: it is a marker showing which star or branch is in a hollow state, its force reduced, so that something tends to become illusory or arrive late.
Mệnh lý tham nguyên by Viên Thụ San (1915) gives the Bát Tự usage: take the cycle of the day pillar; if the day falls in the Giáp Tý cycle, a year or hour branch of Tuất or Hợi is Không vong, and Thìn or Tỵ, the two branches opposite the Không vong pair, is cô hư (lonely and empty)[1].
Why Are There Two Missing Branches in Each Cycle?
The reason lies in the fact that ten stems are not enough to pair with all twelve branches. The ten heavenly stems are Giáp, Ất, Bính, Đinh, Mậu, Kỷ, Canh, Tân, Nhâm, Quý; the twelve earthly branches are Tý, Sửu, Dần, Mão, Thìn, Tỵ, Ngọ, Mùi, Thân, Dậu, Tuất, Hợi. Yang stems pair only with yang branches, and yin stems pair only with yin branches, so each ten-day cycle uses only ten branches, leaving two branches unpaired. Those two unpaired branches change with each cycle, forming six different Không vong pairs. Ngũ hành đại nghĩa by Tiêu Cát of the Sui explains the name: within a cycle, the two branches with no stem to pair with are called cô (lonely), and the two branches opposite them are called hư (empty); because these branches stand alone without a stem, they are called không vong[2].
The counting is very simple: take the stem of the first day of the cycle as the starting point, count forward ten days, and whichever branches do not appear within those ten days are the Không vong. The book Tăng San Bốc Dịch by Dã Hạc lão nhân, in chapter 旬空章第二十六, records all six lines: in the Giáp Tý cycle, Tuất and Hợi are empty; in the Giáp Tuất cycle, Thân and Dậu are empty; in the Giáp Thân cycle, Ngọ and Mùi are empty; in the Giáp Ngọ cycle, Thìn and Tỵ are empty; in the Giáp Thìn cycle, Dần and Mão are empty; in the Giáp Dần cycle, Tý and Sửu are empty[3]. The translation Chu Dịch với Dự Đoán Học by Thiệu Vĩ Hoa and Mạnh Hà also records these same six lines and adds that the empty cycle is a matter of the day marker, that is, of the day the hexagram is cast or the day the chart is set[4].
How Do You Look Up Không Vong in Bát Tự?
Looking up Không vong takes three steps. First, determine the can chi of the day pillar. Second, find which Giáp cycle that day pillar belongs to. Third, compare that cycle's Không vong pair with the other branches of the four pillars; whichever branch matches falls under Không vong.
Tam Mệnh Thông Hội is the Tử Bình book most widely used since the Ming. The summary in the Tứ Khố Toàn Thư edition praises it for gathering older teachings on the meaning of quan, ấn, tài, lộc, thực and thương, on the weight of the useful god, and on the fortune of the various thần sát, while faulting it for favoring the direct officer, direct seal and direct wealth without seeing that their indirect counterparts can also be effective[5]. Không vong is one of those thần sát, so it has to be read alongside the book's other methods.
Table of the Six Không Vong Pairs by Giáp Cycle
The table below is the standard lookup table, used for both Bát Tự and lục hào. The first column is the cycle, the second column is the ten days in the cycle, and the third column is the two Không vong branches.
| Cycle | Ten days in the cycle | Không vong |
|---|---|---|
| Giáp Tý | Giáp Tý, Ất Sửu, Bính Dần, Đinh Mão, Mậu Thìn, Kỷ Tỵ, Canh Ngọ, Tân Mùi, Nhâm Thân, Quý Dậu | Tuất, Hợi |
| Giáp Tuất | Giáp Tuất, Ất Hợi, Bính Tý, Đinh Sửu, Mậu Dần, Kỷ Mão, Canh Thìn, Tân Tỵ, Nhâm Ngọ, Quý Mùi | Thân, Dậu |
| Giáp Thân | Giáp Thân, Ất Dậu, Bính Tuất, Đinh Hợi, Mậu Tý, Kỷ Sửu, Canh Dần, Tân Mão, Nhâm Thìn, Quý Tỵ | Ngọ, Mùi |
| Giáp Ngọ | Giáp Ngọ, Ất Mùi, Bính Thân, Đinh Dậu, Mậu Tuất, Kỷ Hợi, Canh Tý, Tân Sửu, Nhâm Dần, Quý Mão | Thìn, Tỵ |
| Giáp Thìn | Giáp Thìn, Ất Tỵ, Bính Ngọ, Đinh Mùi, Mậu Thân, Kỷ Dậu, Canh Tuất, Tân Hợi, Nhâm Tý, Quý Sửu | Dần, Mão |
| Giáp Dần | Giáp Dần, Ất Mão, Bính Thìn, Đinh Tỵ, Mậu Ngọ, Kỷ Mùi, Canh Thân, Tân Dậu, Nhâm Tuất, Quý Hợi | Tý, Sửu |
Example: a person born on a Giáp Tý day. The day pillar belongs to the Giáp Tý cycle, so Không vong is Tuất and Hợi. If the year, month or hour branch is Tuất or Hợi, that branch falls under Không vong; Mệnh lý tham nguyên names only the year and hour branches[1]. If the four pillars do not contain Tuất and Hợi, then the entire four pillars do not fall under Không vong, although Không vong may still appear in đại vận or lưu niên when that period falls on Tuất or Hợi.
How Does Không Vong Differ from Tuần and Triệt in Tử Vi?
This is the most easily confused point, because all three names carry the meaning "empty." Không vong in Bát Tự is a matter of the ten-day can chi cycle, counted from the day pillar. Tuần and Triệt are concepts of tử vi, counted from the birth year and placed according to palace position.
The book Lý Thuyết Tượng Số by Hoàng Tuấn (2008) explains Tuần Không, also called Tuần Trung Không Vong, as sitting at the six boundary pairs of the twelve earthly palaces, each position being the junction between the end of one Giáp and the beginning of the next Giáp[6]. That way of speaking belongs to tử vi, not Bát Tự, but it helps distinguish them: Không vong in Bát Tự is a consequence of counting can chi, while Tuần and Triệt are star-placement conventions of tử vi.
Do the Schools Agree on Interpreting Không Vong?
They do not agree, and the differences lie in three points.
First, what makes Không vong heavy or light. Tam Mệnh Thông Hội, as quoted in Mệnh lý tham nguyên, reads Không vong together with the life stages: in a stage of growth and prosperity it brings breadth of character and unexpected fame and gain; in a stage of death and extinction it brings repeated success and failure and a drifting life; together with Quý nhân, Hoa cái, Tam kỳ or Trường sinh it indicates great intelligence[1].
Second, whether the two Không vong branches are split. Ngũ hành tinh kỷ by Liêu Trung (1228) quotes the Lâm Khai ngũ mệnh in splitting them by half-cycle: in the Giáp Tý cycle, from Giáp Tý to Mậu Thìn Tuất is Không vong, and from Kỷ Tỵ to Quý Dậu Hợi is Không vong[7]. Most later books do not split them and treat both branches as the Không vong of the whole cycle.
Third, when a void stops counting as void. This belongs to Lục Hào: Tăng San Bốc Dịch records that a prosperous line is not void, a moving line is not void, a line supported by the day or by a moving line is not void, and a moving line that transforms into void or a hidden line that is prosperous is not void either; only a line under month break, a line in phản phục that is controlled, and true void (earth in spring, metal in summer, wood in autumn, fire in winter) count as void[3]. Lý Ngã Bình's commentary in the book likens a moving line on the day or month that transforms into void or break to clouds covering the sun: on the day the void or break is filled, the clouds disperse[3]. The four pillars have no moving lines, so borrowing these rules for Bát Tự should be taken only as a hint about strength.
How Does Tam Mệnh Thông Hội Interpret Không Vong?
Tam Mệnh Thông Hội speaks of Không vong most clearly under Thập ác đại bại (the ten evils and great defeats): within the six Giáp cycles there are ten days whose stem's lộc falls into Không vong, such as Giáp Thìn and Ất Tỵ (Giáp's lộc is Dần and Ất's is Mão, and the Giáp Thìn cycle has Dần and Mão as Không vong) and Nhâm Thân (Nhâm's lộc is Hợi, and the Giáp Tý cycle has Hợi as Không vong). The book says to count it only when seen on the day pillar, and that those who have it are not necessarily unlucky: with auspicious stars and noble influences supporting, it should be read as favorable[8].
The summary in the Tứ Khố Toàn Thư edition also notes that the original book does not name its compiler, giving only Dục Ngô sơn nhân; the Tứ Khố compilers attributed it to Vạn Dân Anh, while the bibliography of the Minh Sử recorded it wrongly as Vạn Dân Dục and Tam Mệnh Hội Thông. The charts of late Ming officials in the book were inserted by later printers and are no longer the old text[5]. So when citing Tam Mệnh Thông Hội, state which edition is cited.
What Should Be Kept in Mind When Reading Không Vong in Practice?
Nhật Nguyệt's suggestion: Không vong is a method of marking degree, not a verdict on destiny. When you see a branch in the four pillars falling under Không vong, what you should do is ask what role that branch plays in the whole chart, whether it receives support, whether it meets clash or combination, and which đại vận it is in. If that branch is prosperous and supported, then by Tam Mệnh Thông Hội's reading Không vong is not necessarily bad[1]. If that branch is declining and overcome, then Không vong is merely one more mark added to an already weak condition.
Two common mistakes should also be avoided. The first is treating Không vong on a branch as a certain sign about marriage, children or money: the original books do not say this, and any such conclusion goes beyond what the books record. The second is treating Không vong as void and ignoring it completely: the original books all use it as a variable, and ignoring it loses a layer of information.
