Excerpted Passages from the Śūraṅgama Sūtra

Original text: 性色真空，性空真色；性水真空，性空真水；性火真空，性空真火；性风真空，性空真风。

Explanation: The earth, water, fire, and wind of the material world (the inanimate environment) are composed of the four great seeds of the tathāgatagarbha; therefore the nature of earth, water, fire, and wind is precisely the nature of the four great seeds. The four great seeds are formless and without marks—they are empty—and thus earth, water, fire, and wind are emptiness (śūnyatā). The nature of the four great seeds is the nature of the tathāgatagarbha; therefore the nature of earth, water, fire, and wind is the nature of the tathāgatagarbha, that is, the wondrous true suchness nature. Because the tathāgatagarbha contains the four great seeds, and the four great seeds can generate the earth, water, fire, and wind of the material world, earth, water, fire, and wind are the nature of the tathāgatagarbha—they are transformed by the tathāgatagarbha through the four great seeds. Thus the tathāgatagarbha contains the nature of earth, water, fire, and wind, and also possesses their properties. The tathāgatagarbha is not earth, water, fire, and wind, yet is precisely earth, water, fire, and wind; the tathāgatagarbha and earth, water, fire, and wind are neither identical nor different.

"Emptiness of nature" refers to the emptiness (śūnyatā) of the tathāgatagarbha. All dharmas born from the tathāgatagarbha are empty in nature and not real; they are generated by a portion of the tathāgatagarbha's seeds flowing forth. Therefore a portion of the tathāgatagarbha becomes form, and the essence of all material form is the true emptiness mind, the tathāgatagarbha. The emptiness mind, the tathāgatagarbha, can produce all forms of appearance; therefore all forms of appearance are also the nature of the tathāgatagarbha. "The nature of form is true emptiness"—the nature and essence of forms of appearance is the tathāgatagarbha, the true emptiness mind of the tathāgatagarbha nature. This is roughly the same as the statement in the Heart Sutra: "form is emptiness (śūnyatā), and emptiness is form." By the same reasoning, water, fire, and wind have this same relationship with the tathāgatagarbha.