首楞嚴義疏注經 10.330

10.330

正顯微細也。識陰離行，故名為湛。不是常住，故云非真。喻急流者，凡夫、二乘全不覺知，十地已前雖覺未盡，故云流急不見。若非想元等者，顯此正是妄想根本，以第八識為界趣生本也。非汝下四句明難斷，互用合開者，寄根明發，故云互用。開令無隔，合為一體也。如前文云「返流全一，六用不行。」開即是合，故無二別。若非證真，此難滅矣。

This directly reveals its subtlety. The aggregate of consciousness is separated from formations, hence it is called "tranquil." It is not permanently abiding, hence it says "is not real." The analogy of the swift current: ordinary persons and followers of the Two Vehicles are entirely unaware of it; even before the tenth bhūmi, though aware of it, they have not fully exhausted it; hence it is said, "the flow is so rapid that it is invisible." As for "If it were not the source of thought," it shows that this is precisely the root of false thoughts, with the eighth consciousness being the source of rebirths in the realms and destinies. The four lines from "Unless your" onward clarify that it is difficult to sever. "Function interchangeably, combining and opening": lodging in the faculties to clarify their emergence, hence it says "interchangeably." Opening causes there to be no barrier; combining makes them a single substance. As the previous text states: "Turning back the flow makes it completely one, and the six functions do not operate." Opening is itself combining, so there is no duality between them. Unless one realizes reality, this is difficult to extinguish.