If the sky has no soil, it can't cover the earth; If there is no soil on the ground, it can't carry everything on the ground, and there is nowhere for grain to grow; Without soil, people can't reproduce naturally without five years.
So heaven and earth can't be soilless. If wood is soilless, it has no power to cultivate; If fire is soilless, it can't shine everywhere; If gold is soilless, it is difficult to be sharp; If water is soilless, it can't flow around by topography. If there is no water and wood in the soil, nothing can grow; Without fire and gold, it cannot thrive. This is the essential truth of the five elements, and the five elements are also constructed from it.