What Does Xu Kong (Empty Line) Mean in Liu Yao? Does a Void Yao Affect the Final Outcome?

Where Does Xu Kong Come From

After casting a hexagram, faced with a page full of yao positions and Earthly Branches, the first place many people get stuck is Xu Kong (empty line / void) — which two Earthly Branches count as void, how to look them up, and why those two.

The origin of Xu Kong is actually straightforward. There are ten Heavenly Stems and twelve Earthly Branches; when paired one-to-one through a full cycle, the Heavenly Stems run out first, leaving two Earthly Branches without a Heavenly Stem partner — those two are the "void" (Kong Wang) for that decade. The sixty Jia Zi cycle is divided into six decades of ten days each, each corresponding to ten Heavenly Stem–Earthly Branch combinations, and the void Earthly Branches differ for each decade:

• Jia Zi decade: Xu and Hai are void
• Jia Xu decade: Shen and You are void
• Jia Shen decade: Wu and Wei are void
• Jia Wu decade: Chen and Si are void
• Jia Chen decade: Yin and Mao are void
• Jia Yin decade: Zi and Chou are void

When casting a hexagram, the decade is determined by the day's Heavenly Stem–Earthly Branch; find the corresponding void pair, then check which of the six yao lines in the hexagram have Earthly Branches matching those two void characters — those are the "Xu Kong yao" (void lines). The method itself is not complicated; in practice it is mechanical and leaves no room for error.

What Does a Void Yao Actually Mean

The traditional saying is "void means unreal" — meaning a void yao lacks sufficient force, its effect temporarily suspended, like knocking on a door when nobody is home.

But there is an important distinction that many introductory resources skip over: whether a void yao is favorable or unfavorable depends entirely on the role that yao plays in the hexagram.

Yong Shen (useful agent) void: The Yong Shen is the core yao you rely on for the matter at hand. Asking about wealth, the wealth yao is the Yong Shen; asking about marriage, the wife-wealth yao or the Guan Gui (officer ghost) yao (when a woman asks about a man) is the Yong Shen. When the Yong Shen falls void, it generally means the matter is difficult to materialize, or the timing has not yet arrived. If the Yong Shen is both void and weak (monthly clash, lacking qi), one can basically judge that the matter will not produce a good outcome in the short term.

Ji Shen (harmful agent) void: The Ji Shen is the yao that restrains the Yong Shen. When the Ji Shen falls void, that is actually a good thing — the restraining force temporarily disappears and the Yong Shen can breathe. In this situation, void is not an obstacle but a temporary relief.

Shi Yao (self line) or Ying Yao (other line) void: The Shi Yao represents the person casting the hexagram; the Ying Yao represents the other party. A void Shi Yao can sometimes be read as the querent's mind being unsettled or their own condition being poor; a void Ying Yao means the other party's attitude is ambiguous or they are temporarily absent. These two situations are especially common when asking about cooperation or relationships; reading them requires looking at the other yao lines together — relying on void alone makes it easy to go astray.

One situation is easy to confuse: Yue Po (monthly clash). Yue Po is when an Earthly Branch is clashed and overcome by the current month's Jian (monthly governor), and it superficially resembles Xu Kong in that both involve "a yao's force being impaired" — but their natures differ. Xu Kong is a temporary emptiness; Yue Po damages the root. The two must not be conflated.

Can Void Be "Broken"? Emerging From Void Is the Key

Xu Kong is not a permanent state; it changes as time passes. This is the concept of "emerging from void" (Chu Kong).

There are two paths to emerging from void:

First, time advances to the next decade, at which point the previously void Earthly Branches regain a Heavenly Stem partner and the void naturally dissolves. For example, in the Jia Zi decade Xu and Hai are void; when the Jia Xu decade arrives, Xu is no longer void.

Second, Chong Shi (clash-filling): if a void yao encounters a day pillar or moving yao whose Earthly Branch clashes with it, the "emptiness" is instead filled solid — this is called "Chong Shi" or "Chong Kong" (clash-filling the void). For example, if a Zi Water yao in the hexagram is void, and the day of action or a moving yao carries Wu Fire (Wu and Zi clash), that Zi Water is actually roused into action, no longer void.

So when reading a hexagram, a void Yong Shen is not necessarily a dead end. Consider: in what time frame is this matter expected to occur? Will the Yong Shen have emerged from void by then? Is there an opportunity for clash-filling?

There is a folk saying: "void that meets a clash turns useful instead" (Kong er feng chong, fan wei you yong) — and that is exactly what this describes. Of course, this only applies when the Yong Shen is originally strong and merely temporarily void. If the Yong Shen is itself weak and rootless, emerging from void still cannot bring the matter to fruition.

A Few Common Misconceptions in Actual Readings

Misconception 1: Seeing void and immediately reading it as inauspicious.

This is the most widespread error. The nature of void must be judged together with the yao's Liu Qin (six kin) role; a void Ji Shen is actually good news. Directly equating "Xu Kong" with "inauspicious" will produce the opposite reading.

Misconception 2: A void Yong Shen means the matter is completely hopeless.

A void Yong Shen only means the timing is not yet ripe — it does not mean the matter will never succeed. Some hexagrams concern events over a longer time horizon; once the Yong Shen emerges from void and regains force, the matter can still turn around. The question is whether one can and should wait — but that is a separate layer of judgment.

Misconception 3: A moving void yao is the same as not having moved.

Opinions here are divided. Some traditional views hold that a moving yao that is also void moves without force and its change does not materialize; other views hold that once a yao moves, its transformation has already occurred and void affects the outcome rather than the process. The latter view is personally preferred — movement is movement; only the result may fall empty or be diminished. It cannot be treated as if no movement occurred. This is a school-of-thought difference, however, and when in doubt it is fine to hold the question open rather than force a definitive answer.

Misconception 4: Looking only at Xu Kong while ignoring Yue Po and Ri Po (daily clash).

Xu Kong is just one dimension of a yao's strength or weakness; the Yue Jian's (monthly governor's) sheng ke (generating and restraining) relationship to a yao is the greatest external force of all. A yao that is strong by monthly command, even if void, still carries force; a yao that is broken and drained by the month, even if not void, can still accomplish little. Xu Kong must be weighed within the whole yao picture and cannot be read in isolation.

A Liu Yao reading is essentially a process of finding the main thread among a set of mutually constraining variables. Xu Kong is one of those variables — its weight is not light, but it holds no veto power. Whether the Yong Shen is timely and strong, how the moving yao transforms, what the Shi-Ying relationship looks like — all of these together form the basis for a final judgment.