Tao: Yin and Yang
The Tao represents the creative principle, as well as the essence, of all which exists in the universe. The matrix and a perpetually moving, and evolving, force. Pure manifest energy and, as such, totally elusive to human perception, limited by duality and the five senses. Lao Tzu, the great Taoist Master, wrote: ‘The Tao I speak of is not the true Tao’. By this, Lao Tzu was referring to the impossibility of communicating the Tao with words. The human intellect relies on a dualistic and discriminating perception and is, thus, incapable of perceiving and estimating the Tao in its wholeness and indivisibility. By this I mean, for example, that light is perceived, through sight, in contrast to darkness (the lack of light), and that this involves an intrinsic polarity (light-dark).
Yin and Yang are nothing but the interpretation of the Tao when it is subjected to intellectual observation. This two opposing aspects, complementary and interdependent, make discrimination and, consequentially, evaluation possible. Nothing can be only Yin or only Yang, in and of itself, if not relatively to something else (or some own intrinsic aspect). It is, rather, the very nature of that which is observed to determine its own relative prevalence of the Yin or the Yang aspect within itself. For example, a body part can be categorised as being Yin or Yang only relatively to another: the abdomen is Yin in relation to the head, but it’s Yang in relation to the feet (see the 'coordinates' outlined below). One can only exist, and thus be observed and estimated, in relation to the other and only ever as the ultimately equal portion of the fundamental wholeness, the Tao.
Yin and Yang: invariable coordinates
The Neijing (a notorious Taoist and TCM* text of antiquity) gives us universal coordinates to categorise the relative prevalence of the Yin or the Yang aspect in that which is observed:
Generally, it can also be said that external or meteorological pathogens (Yang – Heaven) prevalently injure Yin organs, whilst the internal and nutritional (Yin – Earth) ones injure prevalently the Yang organs.
*TCM= Traditional Chinese Medicine.