八識規矩補註 1.20

1.20

This refers to the first five [consciousnesses] comprehending the conventional and seeing emptiness. 'Transform' means transforming and bearing; 'image' refers to the nimittabhāga; 'observe' designates the apprehending darśanabhāga; 'emptiness' designates the apprehended suchness. 'Belongs only to the subsequently attained' excludes the fundamental wisdom, because [the first five] rely exclusively on physical sense-bases. That the subsequently attained wisdom does not directly cognize suchness is because it is a wisdom with conceptual discrimination, and thus cannot directly cognize the non-conceptual principle, arising as it does through deliberation. This emptiness is the vijñaptimātra of actual nature.