The I Ching, which we can well call the experimental foundation of classical Chinese philosophy, is one of the oldest known methods for grasping a situation as a whole and thus placing the details against a cosmic background.

Unlike the Greek-trained Western mind, the Chinese mind does not aim at grasping details for their own sake, but at a view which sees the detail as part of a whole. For obvious reasons, a cognitive operation of this kind is impossible to the unaided intellect. Judgment must therefore rely much more on the irrational functions of consciousness, that is on sensation (the “sens du réel”) and intuition (perception by means of subliminal contents). The I Ching, which we can well call the experimental foundation of classical Chinese philosophy, is one of the oldest known methods for grasping a situation as a whole and thus placing the details against a cosmic background—the interplay of Yin and Yang.

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This grasping of the whole is obviously the aim of science as well, but it is a goal that necessarily lies very far off because science, whenever possible, proceeds experimentally and in all cases statistically. Experiment, however, consists in asking a definite question which excludes as far as possible anything disturbing and irrelevant. It makes conditions, imposes them on Nature, and in this way forces her to give an answer to a question devised by man. She is prevented from answering out of the fullness of her possibilities since these possibilities are restricted as far as practicable. For this purpose there is created in the laboratory a situation which is artificially restricted to the question and which compels Nature to give an unequivocal answer. The workings of Nature in her unrestricted wholeness are completely excluded. If we want to know what these workings are, we need a method of inquiry which imposes the fewest possible conditions, or if possible no conditions at all, and then leaves Nature to answer out of her fullness.
 
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In the laboratory experiment, the known and established procedure forms the stable factor in the statistical compilation and comparison of the results. In the intuitive or “mantic” experiment-with-the-whole, on the other hand, there is no need of any question which imposes conditions and restricts the wholeness of the natural process. It is given every possible chance to express itself. In the I Ching the coins fall just as happens to suit them. ^1)↓ From the point of view of an observer, an unknown question is followed by a rationally unintelligible answer. Thus far the conditions for a total reaction are positively ideal. The disadvantage, however, leaps to the eye: in contrast to the scientific experiment one does not know what has happened. To overcome this drawback, two Chinese sages, King Wên and the Duke of Chou, in the twelfth century before our era, basing themselves on the hypothesis of the unity of nature, sought to explain the simultaneous occurrence of a psychic state with a physical process as an equivalence of meaning. In other words, they supposed that the same living reality was expressing itself in the psychic state as in the physical. But, in order to verify such an hypothesis, some limiting condition was needed in this apparently limitless experiment, namely a definite form of physical procedure, a method or technique which forced nature to answer in even and odd numbers. These, as representatives of Yin and Yang, are found both in the unconscious and in nature in the characteristic form of opposites, as the “mother” and “father” of everything that happens, and they therefore form the tertium comparationis between the psychic inner world and the physical outer world. Thus the two sages devised a method by which an inner state could be represented as an outer one and vice versa. This naturally presupposes an intuitive knowledge of the meaning of each oracle figure. The I Ching, therefore, consists of a collection of sixty-four interpretations in which the meaning of each of the possible Yin-Yang combinations is worked out. These interpretations formulate the inner unconscious knowledge that corresponds to the state of consciousness at the moment, and this psychological situation coincides with the chance results of the method, that is, with the odd and even numbers resulting from the fall of the coins or the division of the yarrow stalks.

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The method, like all divinatory or intuitive techniques, is based on an acausal or synchronistic connective principle. ^2)↓ In practice, as any unprejudiced person will admit, many obvious cases of synchronicity occur during the experiment, which could be rationally and somewhat arbitrarily explained away as mere projections. But if one assumes that they really are what they appear to be, then they can only be meaningful coincidences for which, as far as we know, there is no causal explanation. The method consists either in dividing the forty-nine yarrow stalks into two heaps at random and counting off the heaps by threes and fives, or in throwing three coins six times, each line of the hexagram being determined by the value of obverse and reverse (heads 3, tails 2). The experiment is based on a triadic principle (two trigrams) and contains sixty-four mutations, each corresponding to a psychic situation. These are discussed at length in the text and appended commentaries. There is also a Western method of very ancient origin ^3)↓ which is based on the same general principle as the I Ching, the only difference being that in the West this principle is not triadic but, significantly enough, tetradic, and the result is not a hexagram built up of Yang and Yin lines but sixteen figures composed of odd and even numbers. Twelve of them are arranged, according to certain rules, in the astrological houses. The experiment is based on 4 × 4 lines consisting of a random number of points which the questioner marks in the sand or on paper from right to left. ^4)↓ In true Occidental fashion the combination of all these factors goes into considerably more detail than the I Ching. Here too there are any amount of meaningful coincidences, but they are as a rule harder to understand and therefore less obvious than in the latter. In the Western method, which was known since the thirteenth century as the Ars Geomantica or the Art of Punctation ^5)↓ and enjoyed a widespread vogue, there are no real commentaries, since its use was only mantic and never philosophical like that of the I Ching.
 C. G. Jung from “Synchronicity: An Acausal Connecting Principle.