What Is Hà Lạc Numerology and How Are Hexagrams Cast from Can Chi?

What Is Hà Lạc Numerology?

Hà Lạc numerology is a branch of Eastern divination that takes the Bát Tự four pillars as input, converts can chi into numbers by way of Hà Đồ and Lạc Thư, then converts those numbers into I Ching hexagrams for reading a person's fate. Học Năng's Bát Tự Hà Lạc lược khảo calls Bát Tự the "womb" of Hà Lạc, and conversely says Hà Lạc is Bát Tự transformed^[1]. In other words, to obtain Hà Lạc numbers one must first convert the birth year, month, day, and hour into Bát Tự.

Two distinct layers must be separated. The first is calendrical data: the can chi of the birth year, month, day, and hour together with the accompanying solar terms, which can be calculated and cross-checked against a printed calendar or an independent calculation table. The second is the book's lookup conventions: the numerical values of the can, the numerical values of the chi, the method of converting to hexagrams, and the methods for finding hóa công and thiên địa nguyên khí, which are conventions of the school, not astronomical data. The book puts Bát Tự ahead of Hà Lạc in its title to stress that Hà Lạc, like Mệnh học or Tử Bình, has to begin with the Bát Tự^[1].

Why Is This Subject Named Hà Lạc?

The name Hà Lạc combines the two characters Hà Đồ and Lạc Thư, two ancient diagrams of the I Ching tradition. Bát Tự Hà Lạc lược khảo presents Hà Đồ as tied to the Long Mã and Lạc Thư as tied to the Thần Quy, and says the subject relies on these two diagrams to assign numerical values to can chi. Specifically, only through the intermediary of the five elements in Hà Đồ can chi be converted into numbers, and only through the intermediary of the eight trigrams in Lạc Thư together with the table of ten can paired with hexagrams (nạp giáp) can can be converted into numbers^[1].

The book retells the legend of the Long Mã carrying a diagram out of the Hà river and the divine turtle carrying a writing out of the Lạc river, and itself notes that whether the two creatures really existed lies outside its scope^[1]. This is legend and school convention, not established historical fact. No research has shown that assigning numerical values by Hà Đồ and Lạc Thư has predictive power above chance.

How Are Hà Lạc Hexagrams Cast from Can Chi?

The process consists of three successive transformations. Bát Tự Hà Lạc lược khảo describes this cycle in order: can chi to numbers, numbers to hexagrams, and hexagrams to Hà Lạc hexagrams^[1]. The book also likens this transformation to silkworm eggs hatching into worms, worms becoming pupae, and pupae becoming butterflies, to emphasize that Hà Lạc numbers are born from Bát Tự.

• Step one, establish the four pillars. Convert the birth year, month, day, and hour into the can chi of the four pillars, that is, Bát Tự. This part uses calendrical method and can be looked up in tables. The book specifies that Bát Tự changes the year at the day and hour of the solar term Lập xuân, not on the first day of Tết, and that the birth month also follows the solar terms^[1]. Its appendix contains a hundred-year calendar in Vietnamese, translated from a Chinese calendar, for looking up the can chi of birth days and the solar terms over a hundred years.
• Step two, convert can chi into numbers. Two tables of values are used, one for the can and one for the chi; the table pairing the ten can with trigrams (nạp giáp) explains why each can carries its number. The can chi yield twelve numbers in all; odd numbers are yang and even numbers are yin, and they are arranged separately and added into one yang sum and one yin sum^[1].
• Step three, convert the sums into hexagrams. The book writes: "Only by converting to hexagrams can the meaning be found; left as bare numbers, they tell nothing."^[1]
• Step four, find hóa công, thiên nguyên khí, and địa nguyên khí. Hóa công is taken from the birth month, while thiên nguyên khí and địa nguyên khí are taken from the can chi of the birth year^[1].

Bát Tự Hà Lạc lược khảo includes a practice section that transforms the Bát Tự of each age into Hà Lạc numbers and then into I Ching hexagrams, after which the reader consults the answers to check. This is a rather distinctive presentation: learners transform first and compare afterward.

What Do the Book's Conversion Tables Look Like?

The book gives two tables of values^[1]. Each of the ten can takes the number of the trigram it is paired with on Lạc Thư; the number 5 stands in the middle and goes with no can. Each of the twelve chi takes the pair of generating and completing numbers of its element on Hà Đồ.

The four can give four numbers and the four chi give eight, twelve in all. Odd numbers go into the yang row and even numbers into the yin row, and each row is added up to give a yang sum and a yin sum^[1]. A yang sum above 25 is reduced by 25 and a yin sum above 30 is reduced by 30, once only; 25 is the total of the five odd numbers from 1 to 9 and 30 the total of the five even numbers from 2 to 10. If what remains is 10 or more, the tens are dropped; a round number keeps its tens digit, so 10 keeps 1 and 30 keeps 3^[1]. A yang sum of 25 or less and a yin sum below 30 only drop their tens. Học Năng notes that Hà Lạc Lý Số teaches this passage only briefly, and that the breakdown into cases follows what his teacher handed down^[1].

The remaining number becomes a trigram by the Lạc Thư numbers in the can table: 1 Khảm, 2 Khôn, 3 Chấn, 4 Tốn, 6 Kiền, 7 Đoài, 8 Cấn, 9 Ly. No trigram answers to 5, so the book applies the tam nguyên rule: for a birth in the thượng nguyên a man takes Cấn and a woman Khôn; in the hạ nguyên a man takes Ly and a woman Đoài; in the trung nguyên dương nam and âm nữ take Cấn, while dương nữ and âm nam take Khôn^[1]. The book lists the thượng nguyên as Giáp Tý 1864 to Quý Hợi 1923, the trung nguyên as 1924 to 1983, and the hạ nguyên as 1984 to 2043. For dương nam and âm nữ the trigram from the yang number is placed above and the one from the yin number below; for âm nam and dương nữ it is the reverse. A dương nam is a man born in a year whose can chi are yang, such as Giáp Dần or Bính Thìn; an âm nữ is a woman born in a yin year, such as Ất Mão or Đinh Tỵ^[1].

How Does an Example in the Book Go from Bát Tự to a Hexagram?

The book takes a man whose Bát Tự is the year Quý Sửu, the month Nhâm Tuất, the day Đinh Sửu, and the hour Ất Tỵ^[1]. Recalculated with the two tables above:

The odd numbers are 5, 5, 7, 5, 7, which add up to 29. The even numbers are 2, 10, 6, 10, 10, 2, 2, which add up to 42. 29 less 25 leaves 4, the trigram Tốn (Phong, wind). 42 less 30 leaves 12, and dropping the tens leaves 2, the trigram Khôn (Địa, earth). Quý Sửu is a yin year and the person is a man, so he is âm nam: the trigram from the yin number goes above and the one from the yang number below, giving the hexagram Địa Phong Thăng, as in the book's own solution^[1].

How Do Tiên Thiên and Hậu Thiên Hexagrams Differ?

The Tiên thiên hexagram is the first I Ching hexagram produced from the Bát Tự, like Thăng in the example above; according to the book it governs the earlier part of life. The Hậu thiên hexagram is derived from the Tiên thiên one and governs the later part^[1]. The book warns that Tiên thiên and Hậu thiên here are entirely different from the Tiên thiên and Hậu thiên arrangements of the eight trigrams in the I Ching.

To derive it one must first know the nguyên đường, the line that serves as the focal point of the hexagram; the book compares it to the Mệnh and Thân palaces of Tử Vi^[1]. The nguyên đường is found from the birth hour: for a yang hour (Tý to Tỵ) the count starts with the hour Tý on a yang line, for a yin hour (Ngọ to Hợi) it starts with the hour Ngọ on a yin line, counting from the bottom up, and the nguyên đường sits on the line where the birth hour falls. When the hexagram has only one or two lines of the same kind as the birth hour, they are counted twice over and the count then moves on to the lines of the other kind, once each; with three such lines, two passes cover exactly six hours; with four or five, they are counted once and the count moves on to the other kind. The two pure hexagrams Thuần Kiền and Thuần Khôn have rules of their own, which depend on sex and on whether the birth falls before or after the winter and summer solstices.

In the example above, Tỵ is a yang hour and Thăng has two yang lines, the second and the third. Tý falls on line 2, Sửu on line 3, Dần on line 2 again, and Mão on line 3; moving to the yin lines, Thìn falls on line 1 and Tỵ on line 4. The nguyên đường is on line 4. The change has two parts: the line holding the nguyên đường turns from yin to yang or from yang to yin, and then the lower trigram moves up to become the upper one while the upper trigram moves down^[1]. When line 4 of Thăng turns yang, the upper trigram Khôn becomes Chấn; swapping the two puts Tốn above and Chấn below, giving the Hậu thiên hexagram Phong Lôi Ích, with the nguyên đường now on line 1. The book likewise records Thăng changing into Ích.

Đại vận are also counted from the nguyên đường: age one starts on the nguyên đường line of the Tiên thiên hexagram and the count moves upward, turning back to line 1 after line 6, with nine years for a yang line and six for a yin line; when all six lines are used, it passes to the nguyên đường of the Hậu thiên hexagram and continues in the same way^[1]. For Thăng with the nguyên đường on line 4: line 4 covers ages 1 to 6, line 5 ages 7 to 12, line 6 ages 13 to 18, line 1 ages 19 to 24, line 2 ages 25 to 33, and line 3 ages 34 to 42; passing to Ích, line 1 covers ages 43 to 51 and line 2 ages 52 to 57. The spans 19 to 24, 34 to 42, 43 to 51, and 52 to 57 match the diagram printed in the book.

Do the Same Birth Year, Month, Day, and Hour Always Yield the Same Hexagram?

By the school's convention, two people of the same sex with the same can chi of year, month, day, and hour get the same numbers and the same hexagram, and the book itself turns this into a question. Bát Tự Hà Lạc lược khảo quotes the preface to Trần Hy Di's Hà Lạc Lý Số, noting that I Ching commentators wavered, some holding it to be number, some holding it to be principle, some saying principle precedes number, and others saying principle and number are one. Học Năng adds that Trần Hy Di's book, being titled Hà Lạc Lý Số, naturally holds that principle and number are one^[1].

In the same passage, the book cites a notable figure: according to an old newspaper quoting a United Nations statistician, global population grows by about 5,400 lives per hour, and in the 1957 demographic yearbook they declared that world population had increased by nearly a quarter in twenty years. The book uses this detail to raise the question: countless charts are identical because people were born in the same year, month, day, and hour^[1]. Its answer lies in the word lý: people who share one chart still differ because of birthplace, society, and heredity, which the book places outside the chart. No independent test has shown that this explanation can tell apart people who share the same four pillars.

How Does Hà Lạc Differ from Other Hexagram-Based Subjects?

All use I Ching hexagrams, but Hà Lạc centers on numbers. Bát Tự Hà Lạc lược khảo describes itself as a book of lý số, that is, a practice of the lower, practical part of I Ching philosophy, not a discussion of I Ching theory as the upper, metaphysical part^[1]. In other words, the book does not aim to explain I Ching philosophy but to guide how to obtain Bát Tự and look things up.

As for lineage, Bát Tự Hà Lạc lược khảo states that its foundation is Hà Lạc Lý Số, a book that tradition attributes to Trần Đoàn, also known as Trần Hy Di, but that it translates only the main parts, has its own structure, consults many other books, and contains many passages entirely composed by the compiler^[1]. Học Năng also notes that the tam nguyên table, which runs into the twentieth century, must have been added by a later editor of Hà Lạc Lý Số, since Trần Hy Di had died long before^[1]. This is important when citing: some passages in the book are the words of a later compiler, not of ancient texts. The book also states that it aims at ordinary educated readers and young people, so it tries to avoid Sino-Vietnamese terminology when unnecessary.

What Do You Need to Know to Read a Hà Lạc Hexagram?

Bát Tự Hà Lạc lược khảo sets out the steps for finding hóa công and thiên địa nguyên khí as part of the process, before moving to the interpretive section. An example of interpretation: if a Giáp Tuất or Nhâm Tuất age obtains the Thiên Trạch Lý hexagram, that age has both thiên nguyên khí and địa nguyên khí, because Giáp, Nhâm, and Tuất all belong to Kiền, which is heaven; whereas an Ất Hợi age has only địa nguyên khí, because Hợi belongs to Kiền, which is heaven, while Ất does not. According to the book, thiên nguyên khí and địa nguyên khí govern wealth and honor, so they are also called quan lộc tinh or cáo mệnh tinh^[1]. There are four hóa công, by season of birth: Khảm after the winter solstice and before the spring equinox, Chấn after the spring equinox and before the summer solstice, Ly after the summer solstice and before the autumn equinox, and Đoài after the autumn equinox and before the winter solstice; a chart is said to have hóa công when that trigram appears in its Tiên thiên or Hậu thiên hexagram^[1].

The interpretive section of the book is arranged by each line of each hexagram, and every line has the headings ý hào (meaning of the line), mệnh hợp cách (a fitting fate), mệnh không hợp (an unfitting fate), and xem tuế vận (yearly fortune); the yearly-fortune heading is further split into officials, scholars, and ordinary people^[1]. For line 2 of the Địa Thủy Sư hexagram, for example, the yearly-fortune heading says that officials posted outside are summoned back to the capital and ordinary people receive help from benefactors and succeed. For line 3 of the same hexagram, the book gives the meaning of the line as underestimating the enemy and losing the battle; with a fitting fate, talent and virtue are thin and the people do not submit; with an unfitting fate, the lifespan is not long. These are the book's interpretations, not verifiable data.

Gợi ý của Nhật Nguyệt: if you want to study Hà Lạc numerology, start with the four-pillar step, since it is the only part that can be cross-checked against calendrical data. Treat the number, hexagram, and reading sections as the conventions of a school, to be read for understanding how earlier people organized knowledge, not as a basis for decisions about your own or anyone else's health, money, or marriage.

What Should Be Remembered About Hà Lạc Numerology?

Hà Lạc numerology is a divination system that takes Bát Tự as input, converts can chi into numbers by Hà Đồ and Lạc Thư, then converts numbers into I Ching hexagrams. Học Năng's Bát Tự Hà Lạc lược khảo describes this process as three transformations and places Bát Tự as the common gateway for many subjects such as mệnh học, tử bình, and lưỡng đầu kiềm. The strength of the subject is its tight internal system of conventions; its weakness is that the fate-reading section has no basis for independent verification, and the book's answer to the problem of identical four pillars, that each person's lý differs, has not been independently tested.