Five Phases Theory
Similar to the yin-yang theory, the five-phases theory states that the five natural elements or phases illustrates the different relationships between the zang-fu organs and their characteristics according to their element. In acupuncture, the theory is also used to target “element points” or five transport points located at the hands and feet.
The law of promotion/generation demonstrates the cycle of progression of the five elements in nature and in the human body. In layman’s terms, wood generates fire (like how we light fires with wood), fire generates earth (like the lava of the earth giving rise to earth and soil), earth generates metal (like how precious minerals and metals are deposited in the earth), metal generates water, and water generates wood (like how water can help trees grow).
On the other hand, the law of restriction states that certain elements can limit or control other elements, most often which are opposite them. In this cycle, wood restrains earth (like how a trees roots would penetrate the soil); water restrains fire (like putting out the flames with water); fire restrains metal (like a blacksmith melting metal with fire); and metal restrains wood (like a metal axe would if it was used to cut down a tree).
Since each zang-organ is interconnected with one another because of their ascribed element, a disease of one organ can affect another. In the generation cycle, deficiency would be addressed by tonifying the mother. For example, deficient lung qi (metal) would mean tonifying its promoting element and corresponding organ, which is the spleen (earth), so that the mother (spleen) can nourish the child (lung). However, in the case of excess, cleanse or purge both the organ and its child. For example, excess fire of the heart and liver can be addressed by purging first the heart (fire) in order to clear the liver (wood).
In the restriction cycle, hyperactive zang-organs are treated by suppressing the strong and assisting the weak zang-organs according to the law of restriction. For example, lung yin deficiency with a hyperactive liver means that the liver (wood) is counter-restraining the lung (metal) so the treatment would be to tonify the lung yin and to suppress the liver.