As with many ancient divination techniques it originally began with perceiving patterns in the surrounding environment and at a later date was formalised and commited to writing. Unlike the origins of runes and ogam, I Ching is accredited to an inspired mortal rather than a God, in this case Fu Hsi first emperor of China. The I Ching has went through many ammendments each time becoming more formalised and easier to read.
The I ching consists of the two complementary opposites, yin and yang. These represent odd / even, masculine / feminine, positive / negative, day / night. In ancient times yin was the shaded north side of a hill, whereas yang was the sunny south side. Yang governs all things masculine, positive, heaven, hard, moving and living. Yin governs all things feminine, negative, earthly, soft, static and non-living.
The I ching consist of Yin and Yang but these are said to have gave birth to the four primary symbols. An extra line is then added to each of these symbols to create the eight trigrams which relate to the eight directions of space.
Below are the eight trigrams arranged in the Former Heaven Sequence. To see any of the trigram meanings click on the relevant symbol.