In essence, everything in the universe must be the product of five changes of yin and yang, such as people, animals, plants, minerals, etc., all of which are produced by different states of yin and yang. The five-element attribute of a specific thing can change with the change of time, environment and conditions. For example, the nature of vegetation belongs to wood, and when it burns, it becomes fire;
When an object is located in the east, its nature is wood, and when it is transferred to the south, its nature is fire; A person's character belongs to fire when he is irritable and water when he is weak; From the point of view of movement, the nature of the five elements of things is relatively changed. Because the movement and change of all things are caused by the quantitative change of yin and yang, there must be only five changes in the state of things, and there will never be more or less.
Through long-term contact and observation, the ancient working people realized that each line of the five elements had different performances. "Straight wood is straight" means that wood has the characteristics of growth and rising; "Fire is said to get angry", which means that fire has the characteristics of heating up; "Soil-made crop wall" means that the soil has the characteristics of planting crops and biochemical substances; "Gold says that it changes with leather" is that gold has the characteristic of killing change;
"Moisturizing" means moistening downward. Based on this understanding, the ancients classified all kinds of things in the universe into five elements, so conceptually, they are not wood, fire, earth, gold and water, but abstract attributes shared by a large class of things and phenomena with comparable characteristics. Wood, fire, earth, gold and water can represent many things, such as season, orientation, body parts, industry, people's personality and so on.