教觀綱宗 1.52

1.52

理即者，但中也。真如法性，隨緣不變，在生死而不染，證涅槃而非淨。逈超二邊，不即諸法。故依圓教，判曰但中。

Identity in principle is the exclusive middle. True suchness and the dharma-nature accord with conditions yet do not change; in birth-and-death it is not defiled, and realizing nirvāṇa it is not pure. It far transcends the two extremes and is not identical with all dharmas. Therefore, relying on the complete teaching, it is judged as the exclusive middle.