首楞嚴義疏注經 3.13

3.13

前文雖云因于明暗，為顯根性本無，假他而有，就妄分別而似有因。今以四處推窮，體無生處，故此標也。

Although the previous text said "conditioned by brightness and darkness," that was to reveal that the faculty's nature is originally non-existent and exists depending on another, seeming to have a cause in terms of delusive discrimination. Now, investigating the four locations, its substance has no place of arising; hence this is indicated here.