成唯識論述記 7.65

7.65

述曰：第三又為顯性不定，故置此中「二各二」言。故此二言非解以前所辨諸法，深為有用，能別前故。

The Commentary states: Third, furthermore, in order to demonstrate that their nature is indeterminate, the phrase "two each of two" is set down here. Therefore, these two words do not explain the dharmas distinguished previously; they are profoundly useful because they are able to distinguish [these four] from what came before.