俱舍論記 3.48

3.48

「謂在見道至未知當知」者，答。就中，一約三道以明、二別釋根。此即約見道立未知當知。知者是智，謂在見道十五剎那。八忍、七智，於上、下八諦皆有未曾知當知行轉，故說彼行者名未知當知。問：八忍非智，可言未知當知。七智正知諦理，何故亦名未知當知？解云：七智望緣自諦義邊雖名正智，今望八諦作法，以知八諦猶未周遍、知諦未盡，中間起故，亦名未知當知。

Regarding "Namely, on the path of seeing […] will know what is not yet known": this is the answer. Within this, first, it is explained in terms of the three paths; second, the faculties are explained individually. Here, it is established in terms of the path of seeing as 'one who will know what is not yet known'. 'Knowing' means knowledge, referring to the fifteen moments on the path of seeing. The eight patiences and the seven knowledges, with regard to the eight truths of the higher and lower [realms], all operate in the activity of 'will know what was not yet known'; therefore, that practitioner is called 'one who will know what is not yet known'. Question: The eight patiences are not knowledges, so they may well be called 'will know what is not yet known'. But the seven knowledges correctly know the principle of the truths; why are they also called 'will know what is not yet known'? The explanation says: In terms of taking their own truths as cognitive objects, the seven knowledges are indeed called correct knowledge; but now, proceeding according to the eight truths, because the knowledge of the eight truths is not yet comprehensive and the knowing of the truths is not yet complete, and because they arise in the intermediate stages, they are also called 'will know what is not yet known'.