成唯識論述記 7.239

7.239

述曰：第二翻解也。不能思慮，無尋、伺故；不能自起，藉他引故；緣麁事故，唯外門轉，唯緣外境，不內緣種、根、理等故。有此所以，起藉多緣，境界皆定，各有限故。由所依等，或闕等時，故斷時多，現行乃少。

The Commentary states: This is the second alternative explanation. They cannot deliberate, because they lack coarse examination and subtle investigation; they cannot arise of themselves, because they rely on other [factors] to induce them; because they take coarse matters as objects, they turn only at the external gate, taking only external objects, and do not internally take seeds, sense faculties, principles, etc., as objects. For these reasons, their arising relies on manifold conditions, their domains of objects are fixed, and each has its limitations. Because their bases, and so forth, are sometimes deficient, the times when they are interrupted are many, and their active operation is scarce.