What is the 'Useful God' (Yong Shen) in BaZi (Four Pillars)?

What is the Useful God in Bát Tự (Four Pillars)?

The Useful God (Chinese character: 用神) is the element chosen as the balancing axis for a specific Four Pillars chart. It is not the generally "beautiful" element, but the most useful element for the chart under examination. But to understand why an element is chosen, one must go through the sequence of steps that the Tử Bình (Vietnamese Four Pillars astrology) school uses: read the month command, measure strength and weakness, determine the structure, and only then choose the Useful God by one of four approaches. This article follows exactly that sequence, and at each step states clearly the basis of that step along with its consequences for the next step.

What is the month command and why is it the first measure?

The month command is the earthly branch of the month pillar, that is, the branch standing in the second position of the four pillars. It is regarded as the first measure of strength and weakness because it tells which season holds power.

Basis: each earthly branch corresponds to a month of the year, and each month belongs to a season. The season determines which element is in its proper qi and which element is in decline. A person born in the Hợi or Tý month belongs to winter, when Water qi is at its peak. A person born in the Tỵ or Ngọ month belongs to summer, when Fire qi is at its peak. If the day master is Fire and the person is born in the Hợi month, then from the very starting point it is at a disadvantage, because the season is nurturing Water, and Water controls Fire.

Why not consider the year stem or the day branch first? Because the year stem and the day branch do not carry seasonal information. Only the month command tells the background climate of the chart, so it is step one. The result of this step is a preliminary judgment: whether the day master is in season or out of season. That judgment carries over to step two.

What is strength and weakness and how is it measured?

Strength and weakness is the degree of power of the day master across the whole chart, not just the season. Three criteria are used: obtaining the command, obtaining the ground, and obtaining the force.

Obtaining the command means the day master is supported by the month command, that is, the element of the month branch generates or matches the day master. Obtaining the ground means the day master has roots in the other branches, that is, among the remaining branches there are hidden stems of the same element as the day master or generating it, commonly called having a root. Obtaining the force means the number of stems and branches supporting the day master is greater than the number of stems and branches controlling or draining it.

The basis for adding these together: the month command tells the season, but the season does not tell everything. A day master born out of season can still be strong if the other branches are all its roots. Conversely, a day master that obtains the command can still be weak if it is surrounded on all sides by elements that control or drain it.

The result of this step is one of two labels: strong self or weak self. That label is not yet enough to choose the Useful God, because one must also see which mould the chart falls into. The next step is determining the structure.

What is the structure and what does it name the chart after?

The structure is the mould of the chart, named after whichever god holds the month command and whether it is revealed in the heavenly stems.

Basis: the month command contains one or several hidden stems (stems concealed within the branch). Whichever hidden stem holds power within the month branch is considered first. If that stem is in turn revealed in the heavenly stems, that is, appears openly in one of the four stems, then it is taken as the structure. For example, if the month command is Dần, within Dần are hidden Giáp, Bính, Mậu. If Giáp is revealed in a stem, the chart becomes a structure according to Giáp, and the name of the structure attaches to the ten god role that Giáp plays relative to the day master: Direct Officer structure, Indirect Wealth structure, Eating God structure, and so on.

Why must one pass through this step before choosing the Useful God? Because the structure tells which direction the chart is "running" in. A chart that forms a Following Wealth structure has a direction that goes along with Wealth, not against it. A chart that forms a Direct Officer structure with a weak self is handled differently from a Direct Officer structure with a strong self. Skip the structure and choosing the Useful God is reduced to counting elements, and that is where many people make mistakes.

The result of this step is a name: which structure the chart belongs to. That name, together with the strength label from the previous step, is the input for the four approaches to choosing the Useful God in the sections below.

What are establishing the officer and the yang blade, and why are they treated separately?

Establishing the officer is the case where the officer of the day stem sits exactly in the month branch. The yang blade is the position next after the officer position, and is regarded as stronger than the officer level.

Basis: each heavenly stem has a branch called its officer, that is, the place where that stem obtains qi most strongly according to the officer table. For example, Giáp has its officer in Dần. If a person is born in the Dần month and the day stem is Giáp, then the month branch is precisely the officer of the day stem, called establishing the officer. The next position on the earthly branch cycle, counted in the forward direction of the twelve branches, is Mão for Giáp, and Mão is called the yang blade of Giáp. The yang blade is not the officer, but its qi force is regarded as more taut than the officer: the officer is a place of stable usefulness, the yang blade is a place where qi is compressed to a sharp degree.

Why must establishing the officer and the yang blade be placed in the structure step rather than merged into strength and weakness? Because these two cases take their names directly from the relationship between the day stem and the month branch, exactly the same naming mechanism as the structure: the month command determines the mould of the chart. The difference is that they do not go through hidden stem revealed in stem, but settle immediately on the correlation of stem with branch. The result of this step is a separate structure label: establishing the officer structure or yang blade structure. That label directly affects the step of choosing the Useful God, because establishing the officer and the yang blade usually push the day master toward strength, and the yang blade is further regarded by many schools as needing to be controlled first.

How do the Useful God, the Favorable God and the Unfavorable God differ?

The Useful God is the element chosen to rebalance the chart. The Favorable God is the element that generates and supports the Useful God, that is, the element standing before the Useful God in the generating cycle. The Unfavorable God is the element that destroys the Useful God.

Basis: the relations among the five elements have two directions, generating and controlling. If the Useful God is Wood, then the element that generates Wood is Water, so Water is the Favorable God; the element that controls Wood is Metal, so Metal is the Unfavorable God. The element that Wood generates is Fire, which does not automatically fall into either of the two groups above, because its role depends on what the chosen Useful God is meant to do: if qi needs to be drained, Fire can be useful; if not, it is a neutral element.

Only after distinguishing these three groups can they be used when interpreting the major cycles and annual cycles: encountering an element belonging to the Useful or Favorable God is favorable, encountering an element belonging to the Unfavorable God is adverse. But which element to choose as the Useful God is where there are many approaches, and that is the next part.

What is support and restraint and why is it the most common approach?

Support and restraint is the method of choosing the Useful God by the principle that a weak self is supported and a strong self is restrained. This is the most commonly used approach in practice.

Basis: after the step of measuring strength and weakness, we already have the label of strong self or weak self. If the self is weak, the chart lacks a source of support, so the Useful God is the element that generates the day master (the Resource star) or the element of the same kind as the day master (the Peers and Robbers). If the self is strong, the chart has an excess of source, so the Useful God is the element the day master generates (the Output stars) to drain qi, the element the day master controls (the Wealth star) to expend qi, or the element that controls the day master (the Officer and Seven Killings) to restrain it.

For example: day master Fire, weak self, then Wood generating Fire is the Useful God, or Fire of the same kind is a helper. Day master Fire, strong self, then Earth to drain Fire, Metal to expend Fire, Water to control Fire can all enter the list of candidates, and further steps must be considered to settle it.

Why is it common? Because it needs only one input, the strength label, and requires no additional data. But precisely because it is simple, it does not cover every chart, and that is the reason there are three more approaches.

What is mediation and when is it used?

Mediation is the method of choosing the Useful God when two elements are in balanced mutual control, taking the intermediate element as a bridge.

Basis: in the controlling cycle, Metal controls Wood, Wood controls Earth, Earth controls Water, Water controls Fire, Fire controls Metal. If in the chart there are two opposing elements and neither dominates, choosing one of the two sides as the Useful God will push the chart toward one extreme. The mediation approach chooses the element standing between them in terms of generation: the element that the controlled side generates, and the element that generates the controlling side. For example, if Metal controls Wood in balance, the intermediate element is Water, because Water is generated by Metal and generates Wood. Water both receives the qi of Metal and nurtures Wood, so both sides benefit instead of one side being wiped out.

The result of this step is an element belonging neither to the controlling side nor to the controlled side. It applies only when the two sides are truly balanced; if one side is clearly stronger, one must return to support and restraint.

What is climate adjustment and how does it differ from support and restraint?

Climate adjustment is the method of choosing the Useful God by season: born in winter when it is too cold, Fire is needed; born in summer when it is too hot, Water is needed.

Basis: the month command tells the season, and an extreme season creates a problem that support and restraint does not look at. A chart born in the Tý month (winter, Water at its peak) can have a strong day master, and according to support and restraint it must be restrained, that is, use the element that controls or drains the day master. But if the whole chart is freezing, adding more restraint can make the qi of the chart stagnate. Climate adjustment says: first it must be warmed, that is, use Fire, and only then discuss balance. Conversely, born in the Ngọ month (summer, Fire at its peak) with a dry, hot qi of the chart, Water is needed to cool it.

The core difference: support and restraint looks at the correlation of forces, climate adjustment looks at the climate of the season. The two approaches can yield two different elements on the same chart, and that point is a clash between schools, to be discussed in the section below.

What is disease and remedy and why does it not coincide with support and restraint?

Disease and remedy is the method of choosing the Useful God by finding the most serious fault of the chart and taking the element that treats exactly that spot. The disease is the fault, the remedy is the element that cures it.

Basis: once the structure and the strength label are in hand, we scan to see what is damaging the chart. It may be an element so strong that it overwhelms the whole chart, it may be two elements in fierce clash, it may be a stem that is bound and loses effect, it may be a structure broken by an element coming from another pillar. That breaking spot is the disease. The element capable of blocking or removing that breaking spot is the remedy, that is, the Useful God.

Why does it not coincide with support and restraint? Because support and restraint is derived from the general strength label of the day master, while disease and remedy is derived from the specific fault of the chart. A chart with a strong self according to support and restraint needs restraint, but if the most serious fault lies in another element being squeezed, then the remedy must target that spot first. The two approaches can give two different answers, and the interpreter must choose.

What is the following structure and why is it the exception to support and restraint?

The following structure is a chart in which the day master is so weak that it cannot resist, so one must go along with the dominating element instead of trying to rebalance.

Basis: support and restraint assumes that the day master can still be balanced, that is, there is still room to support or restrain. But there are charts in which the day master has no significant root, while some element occupies almost all stems and branches and no element is strong enough to block it. At that point, bringing in an element that generates and supports the day master creates no counterweight, and is even swallowed by the dominating element. The handling approach reverses direction: take the very element that is dominating as the axis, go along with it. That is the following structure. The specific name attaches to the element followed, for example Following Wealth, Following Killings, Following Output.

Consequence: this is where a wrong interpretation easily goes completely backwards. If a chart is truly a following structure and the interpreter still applies support and restraint, then the Useful God chosen will be opposite to the axis of the chart, and the entire reading of major and annual cycles afterward is inverted. Conversely, if a chart has not reached the following level and the interpreter hastily assigns a following structure, it also goes backwards. Therefore the following structure must be considered a conditional exception, not a default approach.

Why can the four approaches above not be ranked for every chart?

Because the four approaches answer four different questions, and no approach subsumes another. Support and restraint asks about the forces of the day master. Mediation asks about the balance between two opposing elements. Climate adjustment asks about the climate of the season. Disease and remedy asks about the specific fault of the chart. A chart can be at once weak self, born in winter, and have a fault in the year pillar. The three answers can point to three different elements.

The basis for saying they cannot be ranked: there is no common criterion to compare those three answers with one another, because they measure three different quantities. To rank them one would need a common measure, and in Tử Bình there is no such common measure. This is not a place where I am speculating: it is precisely because of the lack of a common measure that the schools split apart.

Where do the Tử Bình schools disagree?

The disagreement is over the order of priority among the four approaches, and at a deeper level, over which approach has the right to override which.

Some schools place support and restraint first, treating climate adjustment as merely an adjusting factor after the Useful God has been chosen by strength and weakness. Some schools place climate adjustment first, holding that climate is the background condition, and that without warming or cooling, all balance calculations are meaningless. Some schools prioritize disease and remedy, holding that the most serious fault must be removed first before discussing the rest. Some schools prioritize the structure, holding that the Useful God must serve the structure already formed, and the other approaches are used only to adjust. As for the following structure, there is greater agreement that it is an exception, but the threshold for determining whether a chart has reached the following level is still not agreed.

Practical consequence: for the same chart, two people following two schools can produce two different Useful Gods, and therefore interpret two different life courses. This is a real disagreement within the Tử Bình tradition, not a small matter. Learners should know this instead of believing that the whole field agrees on a single order.

What can and cannot be inferred from the Useful God?

From the Useful God one can infer the direction for reading major cycles and annual cycles: encountering an element of the Useful or Favorable God is more favorable, encountering an element of the Unfavorable God is more adverse. One can infer a direction for choosing professions, colors and orientations according to the element of the Useful God, at the level of suggestion. One can infer a way of looking at relationships with other people according to the element that person carries.

One cannot infer a certain outcome for a specific year, because major cycles and annual cycles also interact with each other and with the original chart in many ways. One cannot infer matters of wealth or health at the level of assertion. And one cannot infer anything if the step of choosing the Useful God was already wrong, so the entire value of the later sections depends on following the sequence correctly: month command, strength and weakness, structure, and only then the Useful God.

Overview article on the topic: What Is Vietnamese Astrology? An Overview of Reading Methods and Foundational Concepts