TL;DR: Khóa thể are the classification names of individual Lục Nhâm hexagram types, formed from the structure of the four khóa, the three truyền and the relations between can and chi. A Lục Nhâm hexagram has no single proper name; it is called by a combination of khóa thể, for example "Trùng Thẩm, Gian Truyền, Ngưng Âm, Cô Quả". Lục Nhâm đại toàn records the conditions and image text of each khóa thể; Lục Nhâm trực chỉ covers all 720 cục, each with its khóa thể, khóa nghĩa and judgment.
What are Lục Nhâm khóa thể?
Khóa thể are the names given to each type of hexagram, determined from the structure of the four khóa, the three truyền and the relations between can and chi, in order to classify hexagrams for lookup and interpretation. A Lục Nhâm hexagram has no single proper name; it is called by a combination of several khóa thể, for example a hexagram may carry the name "Trùng Thẩm, Gian Truyền, Ngưng Âm, Cô Quả" or "Phục Ngâm, Tự Nhiệm, Nguyên Thai".
The basis for naming lies in four layers of data that the diviner must calculate first: day and hour, the heavenly plate and earthly plate, the four khóa, and the three truyền. Once these four layers are complete, the student compares them with the rules in the books to assign khóa thể, then from khóa thể derives khóa nghĩa and the judgment. Khóa thể acts as a classification label, shortening interpretation time and giving several people discussing one hexagram a common starting point.
How is a Lục Nhâm hexagram named?
A Lục Nhâm hexagram is named by joining the khóa thể recognized from its structure: the first name is the one belonging to the phát dụng (initiating) method used to draw the Sơ truyền (such as Nguyên Thủ, Trùng Thẩm, Hao Thỉ, Phục Ngâm), followed by names from the shape of the three truyền and from the thần sát. Lục Nhâm trực chỉ presents each cục in the same mold: it records the day's can chi, the cục number and the spirit above the can, records "khóa thể" listing the names, records "khóa nghĩa" summarizing the meaning, then gives the "giải" (explanation), the "đoán" (judgment) and sections such as weather, household, marriage, illness, seeking wealth, travellers and warfare; the explanations cite the Khóa kinh, Chỉ chưởng phú and Tâm ấn phú.
For example, in Lục Nhâm trực chỉ, the hexagram for the day Đinh Sửu, eleventh cục, with can above being Dậu, is recorded with the khóa thể "Trùng Thẩm, Gian Truyền, Ngưng Âm, Cô Quả"; the hexagram for the same day, twelfth cục, with can above being Thân, is recorded as "Trùng Thẩm, Tiến Như, Lưu Kim". The same day with two different cục already gives two different combinations of khóa thể, showing that the hexagram name depends on the specific structure, not only on the day.
How are the main khóa thể classified?
Lục Nhâm đại toàn does not divide the khóa thể into groups; it lists sixty-four khóa in a numbered sequence, and the first ten, from Nguyên Thủ to Phản Ngâm, correspond to the nine phát dụng methods in volume one[1]. For easier recall, the names can be gathered by the basis on which they are given, as in the table below.
| Group of khóa thể | Basis of formation | Example names |
|---|---|---|
| By phát dụng method | How the Sơ truyền is drawn from the four khóa | Nguyên Thủ, Trùng Thẩm, Tri Nhất, Thiệp Hại, Hao Thỉ, Phục Ngâm, Phản Ngâm |
| By the shape of the three truyền | Truyền in sequence, with gaps, or all four "mạnh" branches | Gian Truyền, Tiến Như, Ngưng Âm, Lưu Kim, Nguyên Thai |
| By the number of khóa | Some khóa repeat, fewer than four distinct | Bất Bị |
| By thần sát | Start and end of the ten-day week, seasonal cô thần and quả tú | Bế Khẩu, Cô Quả |
These four groups do not exclude one another. A hexagram may carry a name from its phát dụng method, a name from the shape of its three truyền and a name from the thần sát at the same time, so the hexagram name is usually a string of several khóa thể placed side by side.
How do Nguyên Thủ, Trùng Thẩm, Tri Nhất and Thiệp Hại differ?
These four khóa thể correspond to the first three phát dụng methods: tặc khắc, tỷ dụng and thiệp hại. They differ in how many of the four khóa show overcoming and in which direction. According to the Khóa kinh in volume seven of Lục Nhâm đại toàn[1]:
- Nguyên Thủ: exactly one khóa has its upper spirit overcoming its lower spirit, the other khóa have no overcoming ("凡一上克下，余课无克，为元首课"). The book calls it the first of the nine methods and likens it to a ruler governing a minister.
- Trùng Thẩm: exactly one khóa has its lower spirit overcoming its upper spirit, the other khóa have no overcoming ("凡一下贼上，余课无克，为重审课"). The name is explained as the lower offending the upper, like a minister remonstrating with a ruler, who must examine the matter again and again before acting. The judgment for the eleventh cục of the Đinh Sửu day in Lục Nhâm trực chỉ, a Trùng Thẩm chart, contains "bất lợi tiên động", meaning it does not favour making the first move.
- Tri Nhất: two or more khóa show overcoming, and the khóa whose spirit shares the yin or yang of the day stem is chosen to initiate: on a yang day the yang spirit, on a yin day the yin spirit. The name is explained as a matter splitting two ways, where one must know how to choose one.
- Thiệp Hại: several khóa show overcoming and the spirits all share, or all fail to share, the yin or yang of the day stem; the spirit that passes the most overcoming positions on its way from where it stands on the earthly plate back to its home position is then taken ("涉者，度也；害者，克也").
Volume one of the book checks them in order: first a khóa with lower overcoming upper, and only if there is none a khóa with upper overcoming lower ("取课先从下贼呼，如无下贼上克初"); with several overcomings use tỷ dụng, and when tỷ dụng cannot choose use thiệp hại[1].
Why does one hexagram carry several khóa thể at once?
A hexagram carries several khóa thể at once because each khóa thể is determined by a different criterion, and these criteria do not exclude one another. When setting up a hexagram, the student must check in turn: which phát dụng method was used, what shape the three truyền take, whether the four khóa are complete, and where the thần sát stand. Whichever criteria a hexagram satisfies, that khóa thể is added.
For example, in Lục Nhâm trực chỉ, the hexagram for the day Đinh Sửu, eleventh cục, with can above being Dậu, is recorded with four khóa thể: "Trùng Thẩm" from the phát dụng method, "Gian Truyền" and "Ngưng Âm" from the shape of the three truyền (Dậu, Hợi, Sửu, each one branch apart), and "Cô Quả" from the thần sát. These four names do not contradict but complement one another, giving the interpreter enough perspectives before issuing a judgment.
Recording several khóa thể also reflects the reality that a hexagram may be favourable and unfavourable at different layers. The judgment for the twelfth cục of the Đinh Sửu day (Trùng Thẩm, Tiến Như, Lưu Kim) in Lục Nhâm trực chỉ says "quái thể tuy thuận, quái đức tắc nghịch", meaning the form of the hexagram is favourable but its meaning unfavourable, so the interpreter must read all the khóa thể to grasp the whole picture.
How to distinguish khóa thể from khóa nghĩa and the judgment?
Khóa thể is the classification name, khóa nghĩa is the part summarizing the hexagram's meaning, and the judgment is the part interpreted specifically by field. These three parts follow one another in the books' presentation, but they have different roles and should not be confused.
- Khóa thể: lists the recognized names, for example "Trùng Thẩm, Gian Truyền, Ngưng Âm, Cô Quả". This is the lookup part, helping students compare with the general rules.
- Khóa nghĩa: summarizes the hexagram's main meaning in a few short sentences, for example "thân lâm không tử, cầu tài bất hỉ, đinh mã câu phùng, lưỡng quý đồ nhĩ". This is the transition from classification to interpretation.
- Judgment: interprets specifically by field such as weather, household, marriage, illness, seeking wealth, travellers and warfare. This is the application part, depending on the questioner's context.
This layering helps students avoid confusing general rules with a specific judgment. The same khóa thể, in different contexts, may yield different judgments, but the khóa thể name remains unchanged because it rests on the hexagram's structure, not on the question.
Nhật Nguyệt's suggestions for learning Lục Nhâm khóa thể
Nhật Nguyệt's suggestion: beginners should start from the four khóa thể Nguyên Thủ, Trùng Thẩm, Tri Nhất and Thiệp Hại, because they correspond to the first three phát dụng methods and can be checked just by looking at the overcoming within the four khóa. Once familiar, one may expand to the remaining phát dụng methods and to the names from the shape of the three truyền and from the thần sát.
When consulting books, one should choose an edition that records the khóa thể for each hexagram, such as Lục Nhâm trực chỉ with all 720 cục across sixty days, for comparison. Lục Nhâm đại toàn is more suited to looking up general rules and heavenly generals, while Lục Nhâm trực chỉ is suited to looking up each specific hexagram.
Khóa thể should not be regarded as a verdict. Khóa thể is only a classification label; interpretation still depends on context, on the question and on the interpreter's experience. The old books also record many different judgments for the same khóa thể depending on the situation, showing that khóa thể is a starting point, not an ending point.
