成唯識論述記 7.167

7.167

述曰：於中有三：一、證；二、理；三、會。此初也。亦五法中正智所攝，《顯揚》第二等說：正思惟是無漏故。寧知思惟體即是尋？《顯揚》第二、《大論》第二十九皆云：彼正思惟能令心尋求、極尋求、趣入、極趣入等，故有「等」言，尋求者，尋也。

The Commentary states: Herein are three [parts]: 1. proof; 2. reasoning; 3. reconciliation. This is the first. They are also subsumed under correct wisdom among the five phenomena, for fascicle two and other parts of the Prakaraṇāryavācā state that correct thought (samyak-saṃkalpa) is uncontaminated. How is it known that the substance of thought is precisely investigation? Fascicle two of the Prakaraṇāryavācā and fascicle twenty-nine of the Great Treatise both state: 'That correct thought is able to make the mind seek, thoroughly seek, approach, thoroughly approach, and so forth.' Hence the word 'and so forth'; 'seeking' is investigation.