Lecture Notes on the Sūtra of the Collection of the Father and Son (Twenty-Five)

What is the internal water element?

Original text: 大王。云何内水界。谓此身内。所有执受。湿润等性。涎唾脂髓。脓血便利。为内水界。

Explanation: Great King, what is the internal water element? It is all the moistness within the material body, such as saliva, tears, sweat, nasal mucus, fat, pus, blood, urine and feces, and so on — all of these belong to the internal water element.

The earth element is divided into the external earth element and the internal earth element; the internal earth element is the hardness within our material body. The water element is likewise divided into the internal water element and the external water element, and the moistness within the body is the internal water element. The characteristic of water is moistness. For example, when we become emotionally stirred, our eyes well up with tears; even though the tears have not fallen, there is moistness within, and that is the nature of water. When the body gets hot, it sweats; sometimes there are no beads of sweat, yet there is still a sense of dampness — that is the nature of water, and when sweat flows out, that is even more so the nature of water.

There is also water within the skin; if there were no water in the skin, it would become dry and wrinkled, losing its moistness. In fact, there is also a water element in the hair, in the nails, in the bones, and in the flesh; the internal organs all have the nature of water, and the water element pervades the whole body, inside and out. Without the water element, life could not be sustained. Every organ possesses the four great elements — earth, water, fire, and wind — and together they combine to form the various different organs; it is only that the proportions of the four great elements differ from organ to organ. When the proportion of the earth element is large, the material manifests hardness; when the proportion of water is large, moistness and softness manifest. Because the proportions of the four great elements differ, the materials formed are different.