起信論疏筆削記 11.4

11.4

無明為因等者，《楞伽》云：妄想為因，境界為緣，和合而生。疏中用此以科論文，經中妄想即無明也。無明生三細者，下文即展轉相生，今但約根本而言，故云無明為因。

Regarding 'Ignorance is the cause,' etc., the Laṅkāvatāra says: 'Deluded thought is the cause, sense-objects are the condition, and coming together they arise.' The commentary uses this to section the treatise text; in the sūtra, 'deluded thought' is ignorance. As for 'ignorance produces the three subtle marks,' the text below speaks of their producing one another in turn; here it speaks merely in terms of the root, and therefore says 'ignorance is the cause.'