I Ching divination is a form of cleromancy applied to the I Ching. The text of the I Ching consists of 64 hexagrams: six-line figures of yin (broken) or yang (solid) lines, and commentaries on them. There are two main methods of building up the lines of the hexagram, using either 50 yarrow stalks or three coins. Some of the lines may be designated "old" lines, in which case the lines are subsequently changed to create a second hexagram. The text relating to the hexagram(s) and old lines (if any) is studied, and the meanings derived from such study can be interpreted as an oracle.
Methods Each hexagram is six lines, written sequentially one above the other; each of the lines represents a state that is either or , and either old (moving or changing, represented by an "X" written on the middle of a yin line, or a circle written on the middle of a yang line) or young (static, unchanging). The usual methods for consulting the I Ching as an oracle produce a "sacred" or "ritual" number for each type of line: 6 (for an old yin line), 7 (young yang), 8 (young yin), or 9 (old yang). The six lines are produced in order using the chosen method (see below for examples), beginning at the first (lowest) one and proceeding upward to the sixth (uppermost) line, each with its corresponding number. Then, the commentaries applying to the generated hexagram are studied; if the hexagram contains no old lines at all, that concludes the consultation, but if there are one or more old lines, the separate commentary for each such line is also studied. Then, the lines are appropriately changed (any old yin lines into young yang lines, and any old yang lines into young yin lines), which—with the young lines in the original hexagram remaining the same—results in a second, different, hexagram, the commentarial material on which is then also studied.
The method used by the diviner to generate the hexagram(s) depends on their circumstances and beliefs; the yarrow-stalk method is usually employed by traditionalists who find significance in its complexity, and in the resulting time needed to manipulate the stalks to produce a hexagram. Coin methods, and others, are used either by those short of time, or by fortune-tellers who need a quick reading. There are also methods to generate a hexagram by interpreting the time, direction, person, etc., instead of throwing coins or dividing and counting yarrow stalks. Several of the methods described below force exactly one, or no, moving lines; the traditional yarrow-stalk method allows from zero to six moving lines. The yarrow-stalk method favours static lines over moving lines in the ratio 3:1.
Precursor to I Ching: Cracks in turtle shell Plastromancy or the turtle-shell oracle is probably the earliest recorded form of fortune telling. The diviner would apply heat to a piece of a turtle shell (sometimes with a hot poker), and interpret the resulting cracks. The cracks were sometimes annotated with inscriptions, the oldest Chinese writings that have been discovered. This oracle predated the earliest versions of the Zhou Yi (dated from about 1100 BC) by hundreds of years.
A variant on this method was to use ox shoulder bones, a practice called scapulimancy. When thick material was to be cracked, the underside was thinned by carving with a knife.
Yarrow stalks
Hexagrams may be generated by the manipulation of yarrow stalks. These are usually genuine Achillea millefolium stalks that have been cut and prepared for such purposes, or any form of wooden rod or sticks (the quality ranging from cheap hardwood to very expensive red sandalwood, etc.) which are plain, lacquered, or varnished. When genuine Achillea is used, varieties local to the diviner are considered the best, as they would contain qi closer to, and more in tune with, the diviner, or they may come from a particularly spiritual or relevant place, such as on the grounds of a Confucian temple. When not in use, they are kept in a cloth or silk bag/pouch or a wooden case/box.
Fifty yarrow stalks are used, though one stalk is set aside at the beginning and takes no further part in the process of consultation. The remaining forty-nine stalks are roughly sorted into two piles, and then for the right hand pile one stalk is initially "remaindered"; then the pile is "cast off" in lots of four (i.e., groups of four stalks are removed). The remainders from each half are combined (traditionally placed between the fingers of one hand during the counting process) and set aside, with the process then repeated twice (i.e., for a total of three times). The total number of stalks in the remainder pile will necessarily (if the procedure has been followed correctly) be 9 or 5, in the first count, and 8 or 4, in the second. 9 or 8 is assigned a value of 2; 5 or 4, a value of 3. The total of the three passes will be one of just four values: 6 (2+2+2), 7 (2+2+3), 8 (2+3+3), or 9 (3+3+3)—that value is the number of the first line. The forty-nine stalks are then gathered and the entire procedure repeated to generate each of the remaining five lines of the hexagram.
The yarrow-stalk method produces unequal probabilities for obtaining each of the four totals, as shown in the table. Compared to the three-coin method discussed next, the probabilities of the lines produced by the yarrow-stalk method are significantly different.
Number Yarrow-stalk probability Three-coin probability yin or yang Signification Symbol 6 old yin yin changing into yang ---x---8young yinyin, unchanging --- ---9 old yang yang changing into yin ---o---7 young yang yang, unchanging --------
Note that the Yarrow algorithm is a particular algorithm for generating random numbers; while it is named after the yarrow-stalk method of consulting the I Ching, its details are unrelated to it.
Coins
Three-coin method
The three-coin method came into use over a thousand years after the yarrow-stalk method. The quickest, easiest, and most popular method by far, it has largely supplanted yarrow stalks, but produces outcomes with different likelihoods. Three coins are tossed at once; each coin is given a value of 3 or 2, depending upon whether it is heads or tails, respectively. Six such tosses make the hexagram. Some fortune-tellers use an empty tortoise shell to shake the coins in before throwing them on a dish or plate.
Modified Three-coin method The three-coin method can be modified to have the same probabilities as the yarrow-stalk method by having one of the coins be of a second coin type, or in some way be marked as special (i.e., be distinguishable from the other coins). All three coins are tossed at once. The results are counted just as in the original three-coin method, with two exceptions: one to make yin less likely to move, and one to make yang more likely to move. (The probability for 6/8/9/7 in the coin method is 2/6/2/6, but in the yarrow-stalk method is 1/7/3/5; hence, 6 has to occur less often, and 9 has to occur more often.)
In the case where the special coin is tails and the other two are both tails—which would normally produce a 6—re-flip the marked coin: if it remains tails, then it remains a 6 (moving yin); otherwise, treat it as an 8 (static yin). As a 6 can become a 6 or an 8, it reduces the probability of the moving 6. In other words, it makes the old yin less likely to change (or move).
In the case where the special coin is heads and the other two are both tails—which would normally produce a 7—re-flip the marked coin: if it remains heads, then it remains as a 7 (static yang); otherwise, it becomes a 9 (moving yang). As a 7 can become a 7 or an 9, it reduces the probability of the static 7. In other words, it makes the young yang less likely and hence more yangs change as a result.
This method retains the 50% chance of yin:yang, but changes the ratio of moving yin to static yin from 1:3 to 1:7; likewise, it changes the ratio of moving yang to static yang from 1:3 to 3:5, which is the same probabilities as the yarrow-stalk method.
Two-coin method
Some purists contend that there is a problem with the three-coin method because its probabilities differ from the more ancient, yarrow-stalk, method. In fact, over the centuries there have even been other methods used for consulting the oracle.
The two-coin method involves tossing one pair of coins twice: on the first toss, two heads give a value of 2, and anything else is 3; on the second toss, each coin is valued separately, to give a sum from 6 to 9, as above. This results in the same distribution of probabilities as for the yarrow-stalk method.
Simplified two-coin method
A modified version of the two-coin method improves on the original on several aspects. First, while maintaining the probabilities of the traditional yarrow-stalk method, it simplifies outcomes such that they become intuitive at first sight, without need of further calculations. Second, it reduces the average number of coin throws per hexagram by 25%, from 12 to 9. It does so by requiring to throw the coins a second time only if both coins land on the same face (either both heads, or both tails), thus only in 50% of instances. Third, it is easy to memorize, as it clearly identifies heads with yang, and tails with yin, and a greater share of heads/tails with old (aka mature, moving, changing) yang/yin.
The modified two-coin method involves tossing one pair of coins of different size or shape. The larger, or heavier coin is assigned primacy (and is reported here as first, dominant, outcome) while the outcome of the smaller one comes second. Let H be heads and T tails.
If the coins land H, T, yang dominates and the outcome is young yang, unchanging. There is no need to throw the coins again for the same line.
If the coins land T, H, then yin dominates and the outcome is young yin, unchanging. Again, there is no need to throw the coins again for the same line.
If the coins land both on heads (H, H) then the outcome is for sure yang, but one must throw again to verify if the yang is changing (aka old) or unchanging (young). In case the second throw yields at least one H (either H, H, or H, T, or T, H), then the yang is changing. If both coins land on T (T, T) at second throw then the yang is unchanging.
If the coins land both on tails (T, T) then the outcome is for sure yin, but one must throw again to verify if the yin is changing or unchanging. In case the second throw yields both tails (T, T), then the yin is changing. If any of the two coins lands on H (either H, T, or T, H, or H, H) at second throw then the yin is unchanging.
The modified two-coin method yields old yang (changing) 3/16 of the times. Unchanging yang 5/16 times, and unchanging yin 7/16. The remaining 1/16 outcomes is old yin (changing).
It is considered simplified as it reduces the number of throws and calculations needed to correctly identify the outcome of each hexagram line, compared to any other method. While this has its advantages, some purists consider the time required to build the hexagram as a fundamental aspect of I Ching divination, for its ceremonial as well as introspective purposes. This said, any other coin based method can be considered similarly lacking on this regard, when compared to the yarrow-stalk method.
As is the case for the conventional two-coin method and the four coin method, the simplified two-coin method can be boiled down to binary numbers, simply interpreting any H as 1 and any T as 0. Then, old yin takes value of 0000 (0 in decimal numbers), unchanging yin values between 0001 and 0111 (1 to 7), unchanging yang those between 1000 and 1100 (8 to 12), and old yang from 1101 to 1111 (13 to 15). This also clearly showcases the relative probabilities of each outcome.
Four coins