Lectures on the Sūtra of the Collection of the Father and Son (Pitāputrasamāgamanasūtra) (38)

What is the external fire element?

Original text: 云何外火界。谓不执受。温热相生。若复有人。于旷野中。寻求火缘。或以蒿艾。或牛粪屑。或兜罗绵。引火生已。或烧草木。山林聚落。及余方处。皆为所烧。

Explanation: What is the external fire element? It is the mark of temperature and heat that is not singly upheld by one's own tathāgatagarbha, but rather the mark of temperature and warmth jointly upheld by the tathāgatagarbhas of all sentient beings who share common karma—that is the external fire element. If someone seeks the external conditions for making fire in the wilderness, using mugwort, or cow dung, or cotton (tūla), and with a convex lens or a fire-making implement, kindles the fire, once the fire is produced it can burn grass and trees, mountains, forests, villages and settlements, and everything else reachable around it—all can be burned by the great fire.