The I Ching, or Book of Changes, is an ancient Chinese process of divination, whose origin is often estimated as 3,000 BCE, but may have derived thousands of years earlier from the Siberian shamans who used cracked tortoise shells as their method of divining the future. The I Ching is one of the first efforts of the human mind to place itself within the universe; and as it later became a book of wisdom, provided the common source for both Confucianism and the Taoist philosophies. The symbol you have most likely seen is the t'ai chi, a circle divided into light and dark, yang and yin.
This symbol, the t'ai chi, like the Tree of Yggdrasil(the World Tree in the runes), was called the "ridgepole of the world." Astrology uses a similar concept with an imaginary line running from Capricorn through Cancer, (the Mid Heaven to the Nadir), dividing the horoscope into two equal but opposing parts.
Each line has a special meaning based on its placement in the hexagram, which is read from the bottom up. Interestingly enough, it is based on the binary system of 0's and 1's, the same as our modern binary computer languages. The patterns, or oracles, reveal the answer to a psychological, business, social or romantic problem. Coins, sticks, cards, stones can be used, but always in threes. They are tossed into the air and the numerological total determines the type of line in the hexagram, which is built from the base upwards. Your question is best phrased in a "yes-no" form, although it need not be spoken nor written. This process is repeated until the six lines are built. Carl Jung, the psychologist, who called it "synchronicity," formulated the rationality of the answer. This simply means that there is a principle that two separate events will occur at the same time, neither one connected to the other nor having an effect on the other, yet meaningfully related when consciously or subconsciously willed.
Today, there are extensive interpretations: Confucian, Taoist, feminist Goddess, and many other points of view; and since Chinese is an ambiguous language, many authors have claimed a 'newer, more accurate' translation every five months. Whatever works for you, go for it.
Here, however, Brennan has proposed that since the I Ching only hints at the future, and does not actually delineate it because of your free will, there is an important magical use.
He says, "The words 'Know Thyself' were written over the portals of the Greek Mysteries as a reminder that the only real magic works from the inside out, and self-knowledge is an absolute necessity to avoid falling into the snares of self-deception and illusion. If you use the oracle first of all to learn about yourself, then to change yourself, you will find very quickly that you have set yourself on the road to becoming a superior man or woman and the conditions in your external environment will begin to improve accordingly. You will have begun consciously to cooperate with your own evolutionary process, consciously to discharge your accumulated karma. In short, with the aid of the oracle, you will begin to lead a truly magical life."
Brennan has chosen a more dynamic, active astral doorway to pathworking rituals, linking the archetypal symbols in your deep mind with the relevant area of the Astral Plane, and reworded the oracle for the new millennium. For his originality and historical emphasis, I rate this enchanting and immensely readable book, four and a half stars.