Supreme Yang, Lesser Yang, Supreme Yin, Lesser Yin then combine in various ways to form the Ba Gua - the "Eight Symbols" or "Eight Trigrams." In the circles of this diagram are the Chinese names of each of the Trigrams. Each Trigram consists of three lines (hence the name: tri-gram), either broken (the Yin lines) or solid (the Yang lines). The Trigrams in combinations of two make up the 64 hexagrams of the I Ching (Yi Jing) – a principle scripture and divination technique of Taoism.
The ordering of the Eight Trigrams comes in two basic arrangements: the early- or pre-heaven Bagua; and the later- or post-heaven Bagua. The pre-heaven Bagua represents Heavenly influences. The post-heaven Bagua represents Earthly influences. According to Taoism, our job as humans is to align ourselves intelligently (via the principles revealed by the I Ching, and practices such as Feng Shui and Qigong) so that we can derive the greatest benefit from the Heavenly and Earthly influences.
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