成唯識論述記 6.340

6.340

述曰：外人答曰：彼四法無力不能防、修，要待此中別有不逸令其四法，方有防、修之用。故不以四法為防、修體，故知別有不放逸也。

The Commentary states: The opponent answers: 'Those four dharmas have no power and cannot guard and cultivate; they must depend on a separately existing heedfulness within this to direct those four dharmas, and only then do they have the function of guarding and cultivating. Therefore, the four dharmas are not taken as the substance of guarding and cultivating; hence we know that heedfulness exists separately.'